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• C# 5 Async, Part 2: Asynchrony Today

  - by Reed

  The .NET Framework has always supported asynchronous operations.  However, different mechanisms for supporting exist throughout the framework.  While there are at least three separate asynchronous patterns used through the framework, only the latest is directly usable with the new Visual Studio Async CTP.  Before delving into details on the new features, I will talk about existing asynchronous code, and demonstrate how to adapt it for use with the new pattern. The first asynchronous pattern used in the .NET framework was the Asynchronous Programming Model (APM).  This pattern was based around callbacks.  A method is used to start the operation.  It typically is named as BeginSomeOperation.  This method is passed a callback defined as an AsyncCallback, and returns an object that implements IAsyncResult.  Later, the IAsyncResult is used in a call to a method named EndSomeOperation, which blocks until completion and returns the value normally directly returned from the synchronous version of the operation.  Often, the EndSomeOperation call would be called from the callback function passed, which allows you to write code that never blocks. While this pattern works perfectly to prevent blocking, it can make quite confusing code, and be difficult to implement.  For example, the sample code provided for FileStream’s BeginRead/EndRead methods is not simple to understand.  In addition, implementing your own asynchronous methods requires creating an entire class just to implement the IAsyncResult. Given the complexity of the APM, other options have been introduced in later versions of the framework.  The next major pattern introduced was the Event-based Asynchronous Pattern (EAP).  This provides a simpler pattern for asynchronous operations.  It works by providing a method typically named SomeOperationAsync, which signals its completion via an event typically named SomeOperationCompleted. The EAP provides a simpler model for asynchronous programming.  It is much easier to understand and use, and far simpler to implement.  Instead of requiring a custom class and callbacks, the standard event mechanism in C# is used directly.  For example, the WebClient class uses this extensively.  A method is used, such as DownloadDataAsync, and the results are returned via the DownloadDataCompleted event. While the EAP is far simpler to understand and use than the APM, it is still not ideal.  By separating your code into method calls and event handlers, the logic of your program gets more complex.  It also typically loses the ability to block until the result is received, which is often useful.  Blocking often requires writing the code to block by hand, which is error prone and adds complexity. As a result, .NET 4 introduced a third major pattern for asynchronous programming.  The Task<T> class introduced a new, simpler concept for asynchrony.  Task and Task<T> effectively represent an operation that will complete at some point in the future.  This is a perfect model for thinking about asynchronous code, and is the preferred model for all new code going forward.  Task and Task<T> provide all of the advantages of both the APM and the EAP models – you have the ability to block on results (via Task.Wait() or Task<T>.Result), and you can stay completely asynchronous via the use of Task Continuations.  In addition, the Task class provides a new model for task composition and error and cancelation handling.  This is a far superior option to the previous asynchronous patterns. The Visual Studio Async CTP extends the Task based asynchronous model, allowing it to be used in a much simpler manner.  However, it requires the use of Task and Task<T> for all operations.

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• The theory of evolution applied to software

  - by Michel Grootjans

  I recently realized the many parallels you can draw between the theory of evolution and evolving software. Evolution is not the proverbial million monkeys typing on a million typewriters, where one of them comes up with the complete works of Shakespeare. We would have noticed by now, since the proverbial monkeys are now blogging on the Internet ;-) One of the main ideas of the theory of evolution is the balance between random mutations and natural selection. Random mutations happen all the time: millions of mutations over millions of years. Most of them are totally useless. Some of them are beneficial to the evolved species. Natural selection favors the beneficially mutated species. Less beneficial mutations die off. The mutated rabbit doesn't have to be faster than the fox. It just has to be faster than the other rabbits.   Theory of evolution Evolving software Random mutations happen all the time. Most of these mutations are so bad, the new species dies off, or cannot reproduce. Developers write new code all the time. New ideas come up during the act of writing software. The really bad ones don't get past the stage of idea. The bad ones don't get committed to source control. Natural selection favors the beneficial mutated species Good ideas and new code gets discussed in group during informal peer review. Less than good code gets refactored. Enhanced code makes it more readable, maintainable... A good set of traits makes the species superior to others. It becomes widespread A good design tends to make it easier to add new features, easier to understand the current implementations, easier to optimize for performance...thus superior. The best designs get carried over from project to project. They appear in blogs, articles and books about principles, patterns and practices.   Of course the act of writing software is deliberate. This can hardly be called random mutations. Though it sometimes might seem that code evolves through a will of its own ;-) Does this mean that evolving software (evolution) is better than a big design up front (creationism)? Not necessarily. It's a false idea to think that a project starts from scratch and everything evolves from there. Everyone carries his experience of what works and what doesn't. Up front design is necessary, but is best kept simple and minimal, just enough to get you started. Let the good experiences and ideas help to drive the process, whether they come from you or from others, from past experience or from the most junior developer on your team. Once again, balance is the keyword. Balance design up front with evolution on a daily basis. How do you know what balance is right? Through your own experience of what worked and what didn't (here's evolution again). Notes: The evolution of software can quickly degenerate without discipline. TDD is a discipline that leaves little to chance on that part. Write your test to describe the new behavior. Write just enough code to make it behave as specified. Refactor to evolve the code to a higher standard. The responsibility of good design rests continuously on each developers' shoulders. Promiscuous pair programming helps quickly spreading the design to the whole team.

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• Is a university education really worth it for a good programmer?

  - by Jon Purdy

  The title says it all, but here's the personal side of it: I've been doing design and programming for about as long as I can remember. If there's a programming problem, I can figure it out. (Though admittedly StackOverflow has allowed me to skip the figuring out and get straight to the doing in many instances.) I've made games, esoteric programming languages, and widgets and gizmos galore. I'm currently working on a general-purpose programming language. There's nothing I do better than programming. However, I'm just as passionate about design. Thus when I felt leaving high school that my design skills were lacking, I decided to attend university for New Media Design and Imaging, a digital design-related major. For a year, I diligently studied art and programmed in my free time. As the next year progressed, however, I was obligated to take fewer art and design classes and more technical classes. The trouble was of course that these classes were geared toward non-technical students, and were far beneath my skill level at the time. No amount of petitioning could overcome the institution's reluctance to allow me to test out of such classes, and the major offered no promise for any greater challenge in the future, so I took the extreme route: I switched into the technical equivalent of the major, New Media Interactive Development. A lot of my credits moved over into the new major, but many didn't. It would have been infeasible to switch to a more rigorous technical major such as Computer Science, and having tutored Computer Science students at every level here, I doubt I would be exposed to anything that I haven't already or won't eventually find out on my own, since I'm so involved in the field. I'm now on track to graduate perhaps a year later than I had planned, which puts a significant financial strain on my family and my future self. My schedule continues to be bogged down with classes that are wholly unnecessary for me to take. I'm being re-introduced to subjects that I've covered a thousand times over, simply because I've always been interested in it all. And though I succeed in avoiding the cynical and immature tactic of failing to complete work out of some undeserved sense of superiority, I'm becoming increasingly disillusioned by the lack of intellectual stimulation. Further, my school requires students to complete a number of quarters of co-op work experience proportional to their major. My original major required two quarters, but my current requires three, delaying my graduation even more. To top it all off, college is putting a severe strain on my relationship with my very close partner of a few years, so I've searched diligently for co-op jobs in my area, alas to no avail. I'm now in my third year, and approaching that point past which I can no longer handle this. Either I keep my head down, get a degree no matter what it takes, and try to get a job with a company that will pay me enough to do what I love that I can eventually pay off my loans; or I cut my losses now, move wherever there is work, and in six months start paying off what debt I've accumulated thus far. So the real question is: is a university education really more than just a formality? It's a big decision, and one I can't make lightly. I think this is the appropriate venue for this kind of question, and I hope it sticks around for the sake of others who might someday find themselves in similar situations. My heartfelt thanks for reading, and in advance for your help.

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• Removing Barriers to Create Effective Data Models

  After years of creating and maintaining data models, I have started to notice common barriers that decrease the accuracy and usefulness of models. In my opinion, the main causes of these barriers are the lack of knowledge and communication from within a company. The lack of knowledge in regards to data models or data modeling can take many forms. Company Culture Knowledge Whether documented or undocumented, existing business rules of a company can affect how data is modeled. For example, if a company only allows 1 assigned person per customer to be able to manipulate a customer’s record then then a data model that includes an associated table that joins customers and employee’s would be unneeded because that would allow for the possibility of multiple employees to handle a customer because of the potential for a many to many relationship between Customers and Employees. Technical Knowledge Depending on the data modeler’s proficiency in modeling data they can inadvertently cause issues and/or complications with a design without even noticing. It is important that companies share data modeling responsibilities so that the models are developed from multiple perspectives of a system, company and the original problem.  In addition, the tools that a company selects to create data models can also affect the accuracy of the model if designer are not familiar with the tools or the tools are too complex to use for the designer. Existing System Knowledge In order for a data modeler to model data for an existing system so that new changes can be applied to a system then they need to at least know the basic concepts of a system so that they can work within it. This will promote reusability of data and prevent the chance of duplicating data. Project Knowledge This should be pretty obvious, but it is very hard to create an accurate data model without knowing what data needs to be modeled. I have always found it strange that I have been asked to start modeling data prior to a client formalizing any requirements. Usually when this happens I have to make several iterations to a model, and the client still does not know exactly what they want.  In addition additional issues can arise when certain stakeholders of a project are not consulted prior to the design or after the project is over because it can cause miss understandings and confusion by the end user as well as possibly not solving the original problem for which a project is intended to solve. One common thread between each type of knowledge is that they can all be avoided through the use of good communication. For example, if a modeler is new to a company then they should ask older employees about any business specific rules that may be documented or undocumented that must be applied to projects in general. Furthermore, if a modeler is not really familiar with a specific data modeling software then they need to speak up and ask for help form other employees or their manager. This will not only help the modeler in the project, but also help them in future projects that they do for the company. Additionally, if a project is not clearly defined prior to a data modeler being assigned the modeling project then it is their responsibility to communicate with the other stakeholders to clarify any part of a project that is unclear so that the data model that is created is accurately aligned with a project.

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• More Stuff less Fluff

  - by brendonpage

  Originally posted on: http://geekswithblogs.net/brendonpage/archive/2013/11/08/more-stuff-less-fluff.aspxYAGNI – "You Aren't Going To Need It". This is an acronym commonly used in software development to remind developers to only write what they need. This acronym exists because software developers have gotten into the habit of writing everything they need to solve a problem and then everything they think they're going to possibly need in the future. Since we can't predict the future this results in a large portion of the code that we write never being used. That extra code causes unnecessary complexity, which makes it harder to understand and harder to modify when we inevitably have to write something that we didn't think of. I've known about YAGNI for some time now but I never really got it. The words made sense and the idea was clear but the concept never sank in. I was one of those devs who'd happily write a ton of code in the anticipation of future needs. In my mind this was an essential part of writing high quality code. I didn't realise that in doing so I was actually writing low quality code. If you are anything like me you are probably thinking "Lies and propaganda! High quality code needs to be future proof." I agree! But what makes code future proof? If we could see into the future the answer would be simple, code that allows for or meets all future requirements. Since we can't see the future the best we can do is write code that can easily adapt to future requirements, this means writing flexible code. Flexible code is: Fast to understand. Fast to add to. Fast to modify. To be flexible code has to be simple, this means only making it as complex as it needs to be to meet those 3 criteria. That is high quality code. YAGNI! The art is in deciding where to place the seams (abstractions) that will give you flexibility without making decisions about future functionality. Robert C Martin explains it very nicely, he says a good architecture allows you to defer decisions because if you can defer a decision then you have the flexibility to change it. I've recently had a YAGNI experience which brought this all into perspective. I was working on a new project which had multiple clients that connect to a server hosted in the cloud. I was tasked with adding a feature to the desktop client that would allow users to capture items that would then be saved to the cloud. My immediate thought was "Hey we have multiple clients so I should build a web service for these items, that way we can access them from other clients", so I went to work and this is what I created.  I stood back and gazed upon what I'd created with a warm fuzzy feeling. It was beautiful! Then the time came for the team to use the design I'd created for another feature with a new entity. Let's just say that they didn't get the same warm fuzzy feeling that I did when they looked at the design. After much discussion they eventually got it through to me that I'd bloated the design based on an assumption of future functionality. After much more discussion we cut the design down to the following. This design gives us future flexibility with no extra work, it is as complex as it needs to be. It has been a couple of months since this incident and we still haven't needed to access either of the entities from other clients. Using the simpler design allowed us to do more stuff with less stuff!

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• Should I expose IObservable<T> on my interfaces?

  - by Alex

  My colleague and I have dispute. We are writing a .NET application that processes massive amounts of data. It receives data elements, groups subsets of them into blocks according to some criterion and processes those blocks. Let's say we have data items of type Foo arriving some source (from the network, for example) one by one. We wish to gather subsets of related objects of type Foo, construct an object of type Bar from each such subset and process objects of type Bar. One of us suggested the following design. Its main theme is exposing IObservable objects directly from the interfaces of our components. // ********* Interfaces ********** interface IFooSource { // this is the event-stream of objects of type Foo IObservable<Foo> FooArrivals { get; } } interface IBarSource { // this is the event-stream of objects of type Bar IObservable<Bar> BarArrivals { get; } } / ********* Implementations ********* class FooSource : IFooSource { // Here we put logic that receives Foo objects from the network and publishes them to the FooArrivals event stream. } class FooSubsetsToBarConverter : IBarSource { IFooSource fooSource; IObservable<Bar> BarArrivals { get { // Do some fancy Rx operators on fooSource.FooArrivals, like Buffer, Window, Join and others and return IObservable<Bar> } } } // this class will subscribe to the bar source and do processing class BarsProcessor { BarsProcessor(IBarSource barSource); void Subscribe(); } // ******************* Main ************************ class Program { public static void Main(string[] args) { var fooSource = FooSourceFactory.Create(); var barsProcessor = BarsProcessorFactory.Create(fooSource) // this will create FooSubsetToBarConverter and BarsProcessor barsProcessor.Subscribe(); fooSource.Run(); // this enters a loop of listening for Foo objects from the network and notifying about their arrival. } } The other suggested another design that its main theme is using our own publisher/subscriber interfaces and using Rx inside the implementations only when needed. //********** interfaces ********* interface IPublisher<T> { void Subscribe(ISubscriber<T> subscriber); } interface ISubscriber<T> { Action<T> Callback { get; } } //********** implementations ********* class FooSource : IPublisher<Foo> { public void Subscribe(ISubscriber<Foo> subscriber) { /* ... */ } // here we put logic that receives Foo objects from some source (the network?) publishes them to the registered subscribers } class FooSubsetsToBarConverter : ISubscriber<Foo>, IPublisher<Bar> { void Callback(Foo foo) { // here we put logic that aggregates Foo objects and publishes Bars when we have received a subset of Foos that match our criteria // maybe we use Rx here internally. } public void Subscribe(ISubscriber<Bar> subscriber) { /* ... */ } } class BarsProcessor : ISubscriber<Bar> { void Callback(Bar bar) { // here we put code that processes Bar objects } } //********** program ********* class Program { public static void Main(string[] args) { var fooSource = fooSourceFactory.Create(); var barsProcessor = barsProcessorFactory.Create(fooSource) // this will create BarsProcessor and perform all the necessary subscriptions fooSource.Run(); // this enters a loop of listening for Foo objects from the network and notifying about their arrival. } } Which one do you think is better? Exposing IObservable and making our components create new event streams from Rx operators, or defining our own publisher/subscriber interfaces and using Rx internally if needed? Here are some things to consider about the designs: In the first design the consumer of our interfaces has the whole power of Rx at his/her fingertips and can perform any Rx operators. One of us claims this is an advantage and the other claims that this is a drawback. The second design allows us to use any publisher/subscriber architecture under the hood. The first design ties us to Rx. If we wish to use the power of Rx, it requires more work in the second design because we need to translate the custom publisher/subscriber implementation to Rx and back. It requires writing glue code for every class that wishes to do some event processing.

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• Come up with a real-world problem in which only the best solution will do (a problem from Introduction to algorithms) [closed]

  - by Mike

  EDITED (I realized that the question certainly needs a context) The problem 1.1-5 in the book of Thomas Cormen et al Introduction to algorithms is: "Come up with a real-world problem in which only the best solution will do. Then come up with one in which a solution that is “approximately” the best is good enough." I'm interested in its first statement. And (from my understanding) it is asked to name a real-world problem where only the exact solution will work as opposed to a real-world problem where good-enough solution will be ok. So what is the difference between the exact and good enough solution. Consider some physics problem for example the simulation of the fulid flow in the permeable medium. To make this simulation happen some simplyfing assumptions have to be made when deriving a mathematical model. Otherwise the model becomes at least complex and unsolvable. Virtually any particle in the universe has its influence on the fluid flow. But not all particles are equal. Those that form the permeable medium are much more influental than the ones located light years away. Then when the mathematical model needs to be solved an exact solution can rarely be found unless the mathematical model is simple enough (wich probably means the model isn't close to reality). We take an approximate numerical method and after hours of coding and days of verification come up with the program or algorithm which is a solution. And if the model and an algorithm give results close to a real problem by some degree that is good enough soultion. Its worth noting the difference between exact solution algorithm and exact computation result. When considering real-world problems and real-world computation machines I believe all physical problems solutions where any calculations are taken can not be exact because universal physical constants are represented approximately in the computer. Any numbers are represented with the limited precision, at least limited by amount of memory available to computing machine. I can imagine plenty of problems where good-enough, good to some degree solution will work, like train scheduling, automated trading, satellite orbit calculation, health care expert systems. In that cases exact solutions can't be derived due to constraints on computation time, limitations in computer memory or due to the nature of problems. I googled this question and like what this guy suggests: there're kinds of mathematical problems that need exact solutions (little note here: because the question is taken from the book "Introduction to algorithms" the term "solution" means an algorithm or a program, which in this case gives exact answer on each input). But that's probably more of theoretical interest. So I would like to narrow down the question to: What are the real-world practical problems where only the best (exact) solution algorithm or program will do (but not the good-enough solution)? There are problems like breaking of cryptographic ciphers where only exact solution matters in practice and again in practice the process of deciphering without knowing a secret should take reasonable amount of time. Returning to the original question this is the problem where good-enough (fast-enough) solution will do there's no practical need in instant crack though it's desired. So the quality of "best" can be understood in any sense: exact, fastest, requiring least memory, having minimal possible network traffic etc. And still I want this question to be theoretical if possible. In a sense that there may be example of computer X that has limited resource R of amount Y where the best solution to problem P is the one that takes not more than available Y for inputs of size N*Y. But that's the problem of finding solution for P on computer X which is... well, good enough. My final thought that we live in a world where it is required from programming solutions to practical purposes to be good enough. In rare cases really very very good but still not the best ones. Isn't it? :) If it's not can you provide an example? Or can you name any such unsolved problem of practical interest?

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• Python regex to parse text file, get the items in list and count the list

  - by Nemo

  I have a text file which contains some data. I m particularly interested in finding the count of the number of items in v_dims v_dims pattern in my text file looks like this : v_dims={ "Sales", "Product Family", "Sales Organization", "Region", "Sales Area", "Sales office", "Sales Division", "Sales Person", "Sales Channel", "Sales Order Type", "Sales Number", "Sales Person", "Sales Quantity", "Sales Amount" } So I m thinking of getting all the elements in v_dims and dumping them out in a Python list. Then compute the len(mylist) to get the count of the items. The challenge is in getting all the elements of v_dims from my text file and putting them in an empty list. I m particularly interested in items in v_dims in my text file. The text file has data in the form of v_dims pattern i showed in my original post. Some data has nested patterns of v_dims. Thanks. Here's what I have tried and failed. Any help is appreciated. TIA. import re fname = "C:\Users\XXXX\Test.mrk" with open(fname, "r") as fo: content_as_string = fo.read() match = re.findall(r'v_dims={\"(.+?)\"}',content_as_string) Though I have a big text file, Here's a snippet of what's the structure of my text file version "1"; // Computer generated object language file object 'MRKR' "Main" { Data_Type=2, HeaderBlock={ Version_String="6.3 (25)" }, Printer_Info={ Orientation=0, Page_Width=8.50000000, Page_Height=11.00000000, Page_Header="", Page_Footer="", Margin_type=0, Top_Margin=0.50000000, Left_Margin=0.50000000, Bottom_Margin=0.50000000, Right_Margin=0.50000000 }, Marker_Options={ Close_All="TRUE", Hide_Console="FALSE", Console_Left="FALSE", Console_Width=217, Main_Style="Maximized", MDI_Rect={ 0, 0, 892, 1063 } }, Dives={ { Dive="A", Windows={ { View_Index=0, Window_Info={ Window_Rect={ 0, -288, 400, 1008 }, Window_Style="Maximized Front", Window_Name="Theater [Previous Qtr Diveplan-Dive A]" }, Dependent_bool="FALSE", Colset={ Dive_Type="Normal", Dimension_Name="Theater", Action_List={ Actions={ { Action_Type="Select", select_type=5 }, { Action_Type="Select", select_type=0, Key_Names={ "Theater" }, Key_Indexes={ { "AMERICAS" } } }, { Action_Type="Focus", Focus_Rows="True" }, { Action_Type="Dimensions", v_dims={ "Theater", "Product Family", "Division", "Region", "Install at Country Name", "Connect Home Type", "Connect In Type", "SymmConnect Enabled", "Connect Home Refusal Reason", "Sales Order Channel Type", "Maintained By Group", "PS Flag", "Avalanche Flag", "Product Item Family" }, Xtab_Bool="False", Xtab_Flip="False" }, { Action_Type="Select", select_type=5 }, { Action_Type="Select", select_type=0, Key_Names={ "Theater", "Product Family", "Division", "Region", "Install at Country Name", "Connect Home Type", "Connect In Type", "SymmConnect Enabled", "Connect Home Refusal Reason", "Sales Order Channel Type", "Maintained By Group", "PS Flag", "Avalanche Flag" }, Key_Indexes={ { "AMERICAS", "ATMOS", "Latin America CS Division", "37000 CS Region", "Mexico", "", "", "", "", "DIRECT", "EMC", "N", "0" } } } } }, Num_Palette_cols=0, Num_Palette_rows=0 }, Format={ Window_Type="Tabular", Tabular={ Num_row_labels=8 } } } } } }, Widget_Set={ Widget_Layout="Vertical", Go_Button=1, Picklist_Width=0, Sort_Subset_Dimensions="TRUE", Order={ } }, Views={ { Data_Type=1, dbname="Previous Qtr Diveplan", diveline_dbname="Current Qtr Diveplan", logical_name="Current Qtr Diveplan", cols={ { name="Total TSS installs", column_type="Calc[Total TSS installs]", output_type="Number", format_string="." }, { name="TSS Valid Connectivity Records", column_type="Calc[TSS Valid Connectivity Records]", output_type="Number", format_string="." }, { name="% TSS Connectivity Record", column_type="Calc[% TSS Connectivity Record]", output_type="Number" }, { name="TSS Not Applicable", column_type="Calc[TSS Not Applicable]", output_type="Number", format_string="." }, { name="TSS Customer Refusals", column_type="Calc[TSS Customer Refusals]", output_type="Number", format_string="." }, { name="% TSS Refusals", column_type="Calc[% TSS Refusals]", output_type="Number" }, { name="TSS Eligible for Physical Connectivity", column_type="Calc[TSS Eligible for Physical Connectivity]", output_type="Number", format_string="." }, { name="TSS Boxes with Physical Connectivty", column_type="Calc[TSS Boxes with Physical Connectivty]", output_type="Number", format_string="." }, { name="% TSS Physical Connectivity", column_type="Calc[% TSS Physical Connectivity]", output_type="Number" } }, dim_cols={ { name="Model", column_type="Dimension[Model]", output_type="None" }, { name="Model", column_type="Dimension[Model]", output_type="None" }, { name="Connect In Type", column_type="Dimension[Connect In Type]", output_type="None" }, { name="Connect Home Type", column_type="Dimension[Connect Home Type]", output_type="None" }, { name="SymmConnect Enabled", column_type="Dimension[SymmConnect Enabled]", output_type="None" }, { name="Theater", column_type="Dimension[Theater]", output_type="None" }, { name="Division", column_type="Dimension[Division]", output_type="None" }, { name="Region", column_type="Dimension[Region]", output_type="None" }, { name="Sales Order Number", column_type="Dimension[Sales Order Number]", output_type="None" }, { name="Product Item Family", column_type="Dimension[Product Item Family]", output_type="None" }, { name="Item Serial Number", column_type="Dimension[Item Serial Number]", output_type="None" }, { name="Sales Order Deal Number", column_type="Dimension[Sales Order Deal Number]", output_type="None" }, { name="Item Install Date", column_type="Dimension[Item Install Date]", output_type="None" }, { name="SYR Last Dial Home Date", column_type="Dimension[SYR Last Dial Home Date]", output_type="None" }, { name="Maintained By Group", column_type="Dimension[Maintained By Group]", output_type="None" }, { name="PS Flag", column_type="Dimension[PS Flag]", output_type="None" }, { name="Connect Home Refusal Reason", column_type="Dimension[Connect Home Refusal Reason]", output_type="None", col_width=177 }, { name="Cust Name", column_type="Dimension[Cust Name]", output_type="None" }, { name="Sales Order Channel Type", column_type="Dimension[Sales Order Channel Type]", output_type="None" }, { name="Sales Order Type", column_type="Dimension[Sales Order Type]", output_type="None" }, { name="Part Model Key", column_type="Dimension[Part Model Key]", output_type="None" }, { name="Ship Date", column_type="Dimension[Ship Date]", output_type="None" }, { name="Model Number", column_type="Dimension[Model Number]", output_type="None" }, { name="Item Description", column_type="Dimension[Item Description]", output_type="None" }, { name="Customer Classification", column_type="Dimension[Customer Classification]", output_type="None" }, { name="CS Customer Name", column_type="Dimension[CS Customer Name]", output_type="None" }, { name="Install At Customer Number", column_type="Dimension[Install At Customer Number]", output_type="None" }, { name="Install at Country Name", column_type="Dimension[Install at Country Name]", output_type="None" }, { name="TLA Serial Number", column_type="Dimension[TLA Serial Number]", output_type="None" }, { name="Product Version", column_type="Dimension[Product Version]", output_type="None" }, { name="Avalanche Flag", column_type="Dimension[Avalanche Flag]", output_type="None" }, { name="Product Family", column_type="Dimension[Product Family]", output_type="None" }, { name="Project Number", column_type="Dimension[Project Number]", output_type="None" }, { name="PROJECT_STATUS", column_type="Dimension[PROJECT_STATUS]", output_type="None" } }, Available_Columns={ "Total TSS installs", "TSS Valid Connectivity Records", "% TSS Connectivity Record", "TSS Not Applicable", "TSS Customer Refusals", "% TSS Refusals", "TSS Eligible for Physical Connectivity", "TSS Boxes with Physical Connectivty", "% TSS Physical Connectivity", "Total Installs", "All Boxes with Valid Connectivty Record", "% All Connectivity Record", "Overall Refusals", "Overall Refusals %", "All Eligible for Physical Connectivty", "Boxes with Physical Connectivity", "% All with Physical Conectivity" }, Remaining_columns={ { name="Total Installs", column_type="Calc[Total Installs]", output_type="Number", format_string="." }, { name="All Boxes with Valid Connectivty Record", column_type="Calc[All Boxes with Valid Connectivty Record]", output_type="Number", format_string="." }, { name="% All Connectivity Record", column_type="Calc[% All Connectivity Record]", output_type="Number" }, { name="Overall Refusals", column_type="Calc[Overall Refusals]", output_type="Number", format_string="." }, { name="Overall Refusals %", column_type="Calc[Overall Refusals %]", output_type="Number" }, { name="All Eligible for Physical Connectivty", column_type="Calc[All Eligible for Physical Connectivty]", output_type="Number" }, { name="Boxes with Physical Connectivity", column_type="Calc[Boxes with Physical Connectivity]", output_type="Number" }, { name="% All with Physical Conectivity", column_type="Calc[% All with Physical Conectivity]", output_type="Number" } }, calcs={ { name="Total TSS installs", definition="Total[Total TSS installs]", ts_flag="Not TS Calc" }, { name="TSS Valid Connectivity Records", definition="Total[PS Boxes w/ valid connectivity record (1=yes)]", ts_flag="Not TS Calc" }, { name="% TSS Connectivity Record", definition="Total[PS Boxes w/ valid connectivity record (1=yes)] /Total[Total TSS installs]", ts_flag="Not TS Calc" }, { name="TSS Not Applicable", definition="Total[Bozes w/ valid connectivity record (1=yes)]-Total[Boxes Eligible (1=yes)]-Total[TSS Refusals]", ts_flag="Not TS Calc" }, { name="TSS Customer Refusals", definition="Total[TSS Refusals]", ts_flag="Not TS Calc" }, { name="% TSS Refusals", definition="Total[TSS Refusals]/Total[PS Boxes w/ valid connectivity record (1=yes)]", ts_flag="Not TS Calc" }, { name="TSS Eligible for Physical Connectivity", definition="Total[TSS Eligible]-Total[Exception]", ts_flag="Not TS Calc" }, { name="TSS Boxes with Physical Connectivty", definition="Total[PS Physical Connectivity] - Total[PS Physical Connectivity, SymmConnect Enabled=\"Capable not enabled\"]", ts_flag="Not TS Calc" }, { name="% TSS Physical Connectivity", definition="Total[Boxes w/ phys conn]/Total[Boxes Eligible (1=yes)]", ts_flag="Not TS Calc" }, { name="Total Installs", definition="Total[Total Installs]", ts_flag="Not TS Calc" }, { name="All Boxes with Valid Connectivty Record", definition="Total[Bozes w/ valid connectivity record (1=yes)]", ts_flag="Not TS Calc" }, { name="% All Connectivity Record", definition="Total[Bozes w/ valid connectivity record (1=yes)]/Total[Total Installs]", ts_flag="Not TS Calc" }, { name="Overall Refusals", definition="Total[Overall Refusals]", ts_flag="Not TS Calc" }, { name="Overall Refusals %", definition="Total[Overall Refusals]/Total[Bozes w/ valid connectivity record (1=yes)]", ts_flag="Not TS Calc" }, { name="All Eligible for Physical Connectivty", definition="Total[Boxes Eligible (1=yes)]-Total[Exception]", ts_flag="Not TS Calc" }, { name="Boxes with Physical Connectivity", definition="Total[Boxes w/ phys conn]-Total[Boxes w/ phys conn,SymmConnect Enabled=\"Capable not enabled\"]", ts_flag="Not TS Calc" }, { name="% All with Physical Conectivity", definition="Total[Boxes w/ phys conn]/Total[Boxes Eligible (1=yes)]", ts_flag="Not TS Calc" } }, merge_type="consolidate", merge_dbs={ { dbname="connectivityallproducts.mdl", diveline_dbname="/DI_PSREPORTING/connectivityallproducts.mdl" } }, skip_constant_columns="FALSE", categories={ { name="Geography", dimensions={ "Theater", "Division", "Region", "Install at Country Name" } }, { name="Mappings and Flags", dimensions={ "Connect Home Type", "Connect In Type", "SymmConnect Enabled", "Connect Home Refusal Reason", "Sales Order Channel Type", "Maintained By Group", "Customer Installable", "PS Flag", "Top Level Flag", "Avalanche Flag" } }, { name="Product Information", dimensions={ "Product Family", "Product Item Family", "Product Version", "Item Description" } }, { name="Sales Order Info", dimensions={ "Sales Order Deal Number", "Sales Order Number", "Sales Order Type" } }, { name="Dates", dimensions={ "Item Install Date", "Ship Date", "SYR Last Dial Home Date" } }, { name="Details", dimensions={ "Item Serial Number", "TLA Serial Number", "Part Model Key", "Model Number" } }, { name="Customer Infor", dimensions={ "CS Customer Name", "Install At Customer Number", "Customer Classification", "Cust Name" } }, { name="Other Dimensions", dimensions={ "Model" } } }, Maintain_Category_Order="FALSE", popup_info="false" } } };

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• Can I use a single DateTime field on the Entity Framework model side when the value is stored in a set of Int fields in the actual database?

  - by Ivan

  The actual table in the database has separate integer fields for storing year, month, day, hour and minute values (all in UTC) (seconds and milliseconds are irrelevant for my task and considered equal to zero). Needless to say it would be of great convenience to have just one field of DateTime type on the application side and hide all the conversion under the cover of the Entity Framework model code. Any directions on how to do that? I am not very experienced with Entity Framework yet.

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• How to retrieve value from DropDownListFor html helper in ASP>NET MVC2?

  - by Eedoh

  Hello I know there was few similar questions here about DropDownListFor, but neither helped me... I use Entity Framework as ORM in my project. There's EF model called "Stete". Stete has Foreign on EF model called "Drustva" Now I'm trying to make a form for editing the data, for Stete model. I managed to display everything, including Stete.Drustva.Naziv property, but I can't get this last property in my handler method [HttpPost]. It always return 0, no matter what I select in drop down list. Here's the code: DrustvaController: public static IEnumerable<SelectListItem> DrustvaToSelectListItemsById(this KnjigaStetnikaEntities pEntities, int Id) { IEnumerable<Drustva> drustva = (from d in pEntities.Drustva select d).ToList(); return drustva.OrderBy(drustvo => drustvo.Naziv).Select(drustvo => new SelectListItem { Text = drustvo.Naziv, Value = drustvo.Id.ToString(), Selected = (drustvo.Id == Id)? true : false }); } SteteController: private IEnumerable<SelectListItem> privremenaListaDrustava(int Id) { using (var ctx = new KnjigaStetnikaEntities()) { return ctx.DrustvaToSelectListItemsById(Id); } } public ActionResult IzmijeniPodatkeStete(Int32 pBrojStete) { PretragaStetaModel psm = new PretragaStetaModel(); ViewData["drustva"] = privremenaListaDrustava(psm.VratiStetuPoBrojuStete(pBrojStete).Drustva.Id); ViewData.Model = new Models.Stete(); return View("EditView", (Stete.Models.Stete)psm.GetSteta(pBrojStete)); } EditView: <div class="editor-label"> <%: Html.Label("Društvo") %> </div> <div class="editor-field"> <%: Html.DropDownListFor(m => m.Drustva.Naziv, ViewData["drustva"] as IEnumerable<SelectListItem>) %> <%: Html.ValidationMessageFor(model => model.FKDrustvo) %> </div> I am sorry for not translating names of the objects into english, but they hardly have appropriate translation. If necessary, I can try creating similar example...

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• Django 1.2 + South 0.7 + django-annoying's AutoOneToOneField leads to TypeError: 'LegacyConnection'

  - by konrad

  I'm using Django 1.2 trunk with South 0.7 and an AutoOneToOneField copied from django-annoying. South complained that the field does not have rules defined and the new version of South no longer has an automatic field type parser. So I read the South documentation and wrote the following definition (basically an exact copy of the OneToOneField rules): rules = [ ( (AutoOneToOneField), [], { "to": ["rel.to", {}], "to_field": ["rel.field_name", {"default_attr": "rel.to._meta.pk.name"}], "related_name": ["rel.related_name", {"default": None}], "db_index": ["db_index", {"default": True}], }, ) ] from south.modelsinspector import add_introspection_rules add_introspection_rules(rules, ["^myapp"]) Now South raises the following error when I do a schemamigration. Traceback (most recent call last): File "manage.py", line 11, in <module> execute_manager(settings) File "django/core/management/__init__.py", line 438, in execute_manager utility.execute() File "django/core/management/__init__.py", line 379, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "django/core/management/base.py", line 196, in run_from_argv self.execute(*args, **options.__dict__) File "django/core/management/base.py", line 223, in execute output = self.handle(*args, **options) File "South-0.7-py2.6.egg/south/management/commands/schemamigration.py", line 92, in handle (k, v) for k, v in freezer.freeze_apps([migrations.app_label()]).items() File "South-0.7-py2.6.egg/south/creator/freezer.py", line 33, in freeze_apps model_defs[model_key(model)] = prep_for_freeze(model) File "South-0.7-py2.6.egg/south/creator/freezer.py", line 65, in prep_for_freeze fields = modelsinspector.get_model_fields(model, m2m=True) File "South-0.7-py2.6.egg/south/modelsinspector.py", line 322, in get_model_fields args, kwargs = introspector(field) File "South-0.7-py2.6.egg/south/modelsinspector.py", line 271, in introspector arg_defs, kwarg_defs = matching_details(field) File "South-0.7-py2.6.egg/south/modelsinspector.py", line 187, in matching_details if any([isinstance(field, x) for x in classes]): TypeError: 'LegacyConnection' object is not iterable Is this related to a recent change in Django 1.2 trunk? How do I fix this? I use this field as follows: class Bar(models.Model): foo = AutoOneToOneField("foo.Foo", primary_key=True, related_name="bar") For reference the field code from django-tagging: class AutoSingleRelatedObjectDescriptor(SingleRelatedObjectDescriptor): def __get__(self, instance, instance_type=None): try: return super(AutoSingleRelatedObjectDescriptor, self).__get__(instance, instance_type) except self.related.model.DoesNotExist: obj = self.related.model(**{self.related.field.name: instance}) obj.save() return obj class AutoOneToOneField(OneToOneField): def contribute_to_related_class(self, cls, related): setattr(cls, related.get_accessor_name(), AutoSingleRelatedObjectDescriptor(related))

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• DRY Validation with MVC2

  - by Matthew

  Hi All, I'm trying to figure out how I can define validation rules for my domain objects in one single location within my application but have run in to a snag... Some background: My location has several parts: - Database - DAL - Business Logic Layer - SOAP API Layer - MVC website The MVC website accesses the database via the SOAP API, just as third parties would. We are using server and and client side validation on the MVC website as well as in the SOAP API Layer. To avoid having to manually write client side validation we are implementing strongly typed views in conjunction with the Html.TextBoxFor and Html.ValidationMessageFor HTML helpers, as shown in Step 3 here. We also create custom models for each form where one form takes input for multiple domain objects. This is where the problem begins, the HTML helpers read from the model for the data annotation validation attributes. In most cases our forms deal with multiple domain objects and you can't specify more than one type in the <%@Page ... Inherits="System.Web.Mvc.ViewPage" % page directive. So we are forced to create a custom model class, which would mean duplicating validation attributes from the domain objects on to the model class. I've spent quite some time looking for workarounds to this, such has referencing the same MetadataType from both the domain class and the custom MVC models, but that won't work for several reasons: You can only specify one MetadataType attribute per class, so its a problem if a model references multiple domain objects, each with their own metadata type. The data annotation validation code throws an exception if the model class doesn't contain a property that is specified in the referenced MetadataType which is a problem with the model only deals with a subset of the properties for a given domain object. I've looked at other solutions as well but to no avail. If anyone has any ideas on how to achieve a single source for validation logic that would work across MVC client and server side validation functionality and other locations (such as my SOAP API) I would love to hear it! Thanks in advance, Matthew

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• C#: Delegate syntax?

  - by Rosarch

  I'm developing a game. I want to have game entities each have their own Damage() function. When called, they will calculate how much damage they want to do: public class CombatantGameModel : GameObjectModel { public int Health { get; set; } /// <summary> /// If the attack hits, how much damage does it do? /// </summary> /// <param name="randomSample">A random value from [0 .. 1]. Use to introduce randomness in the attack's damage.</param> /// <returns>The amount of damage the attack does</returns> public delegate int Damage(float randomSample); public CombatantGameModel(GameObjectController controller) : base(controller) {} } public class CombatantGameObject : GameObjectController { private new readonly CombatantGameModel model; public new virtual CombatantGameModel Model { get { return model; } } public CombatantGameObject() { model = new CombatantGameModel(this); } } However, when I try to call that method, I get a compiler error: /// <summary> /// Calculates the results of an attack, and directly updates the GameObjects involved. /// </summary> /// <param name="attacker">The aggressor GameObject</param> /// <param name="victim">The GameObject under assault</param> public void ComputeAttackUpdate(CombatantGameObject attacker, CombatantGameObject victim) { if (worldQuery.IsColliding(attacker, victim, false)) { victim.Model.Health -= attacker.Model.Damage((float) rand.NextDouble()); // error here Debug.WriteLine(String.Format("{0} hits {1} for {2} damage", attacker, victim, attackTraits.Damage)); } } The error is: 'Damage': cannot reference a type through an expression; try 'HWAlphaRelease.GameObject.CombatantGameModel.Damage' instead What am I doing wrong?

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• How to retrieve value from DropDownListFor html helper in ASP.NET MVC2?

  - by Eedoh

  Hello I know there was few similar questions here about DropDownListFor, but neither helped me... I use Entity Framework as ORM in my project. There's EF model called "Stete". Stete has Foreign on EF model called "Drustva" Now I'm trying to make a form for editing the data, for Stete model. I managed to display everything, including Stete.Drustva.Naziv property, but I can't get this last property in my handler method [HttpPost]. It always return 0, no matter what I select in drop down list. Here's the code: DrustvaController: public static IEnumerable<SelectListItem> DrustvaToSelectListItemsById(this KnjigaStetnikaEntities pEntities, int Id) { IEnumerable<Drustva> drustva = (from d in pEntities.Drustva select d).ToList(); return drustva.OrderBy(drustvo => drustvo.Naziv).Select(drustvo => new SelectListItem { Text = drustvo.Naziv, Value = drustvo.Id.ToString(), Selected = (drustvo.Id == Id)? true : false }); } SteteController: private IEnumerable<SelectListItem> privremenaListaDrustava(int Id) { using (var ctx = new KnjigaStetnikaEntities()) { return ctx.DrustvaToSelectListItemsById(Id); } } public ActionResult IzmijeniPodatkeStete(Int32 pBrojStete) { PretragaStetaModel psm = new PretragaStetaModel(); ViewData["drustva"] = privremenaListaDrustava(psm.VratiStetuPoBrojuStete(pBrojStete).Drustva.Id); ViewData.Model = new Models.Stete(); return View("EditView", (Stete.Models.Stete)psm.GetSteta(pBrojStete)); } EditView: <div class="editor-label"> <%: Html.Label("Društvo") %> </div> <div class="editor-field"> <%: Html.DropDownListFor(m => m.Drustva.Naziv, ViewData["drustva"] as IEnumerable<SelectListItem>) %> <%: Html.ValidationMessageFor(model => model.FKDrustvo) %> </div> I am sorry for not translating names of the objects into english, but they hardly have appropriate translation. If necessary, I can try creating similar example...

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• ASP.NET MVC Page - hyper links in HTML.ValidationSummary

  - by Rita

  Hi I have Registration page and if the validation fails, it displays the error messages using HTML.ValidationSummary control. Now i have to display the Hyperlink in that Validation Error Message. But it is treating href also as string. The Validation Message that I am trying to display with hyperlink is: **"User already exists in the system, please <a href='../Login.aspx'>login</a>"** Appreciate your responses. Here is my Code: <% using (Html.BeginForm()) {%> <%= Html.ValidationSummary(false) %> <fieldset> <div class="cssform">; <p> <%= Html.LabelFor(model => model.email)%><em>*</em> <%= Html.TextBoxFor(model => model.email, new { @class = "required email" })%> <%= Html.ValidationMessageFor(model => model.email)%> </p> <p> <%= Html.Label("Confirm email")%><em>*</em> <%= Html.TextBox("confirm_email")%> <%= Html.ValidationMessage("confirm_email") %> </p> <p> <%= Html.Label("Password")%><em>*</em> <%= Html.Password("Password", null, new { @class = "required" })%> <%= Html.ValidationMessage("Password")%><br /> (Note: Password should be minimum 6 characters) </p> <p> <%= Html.Label("Confirm Password")%><em>*</em> <%= Html.Password("confirm_password")%> <%= Html.ValidationMessage("confirm_password") %> </p><hr /> <% } %

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• InvalidCastException for two Objects of the same type

  - by LLEA

  hi, I have this weird problem that I cannot handle myself. A class in the model of my mvp-project designed as singleton causes an InvalidCastException. The source of error is found in this code line where the deserialised object is assigned to the instance variable of the class: engineObject = (ENGINE)xSerializer.Deserialize(str); It occurs whenever I try to add one of my UserControls to a Form or to a different UC. All of my UCs have a special presenter that access the above mentioned instance variable of the singleton class. This is what I get when trying to add a UC somewhere: 'System.TypeInitializationException: The type initializer for 'MVP.Model.EngineData' threw an exception. ---- System.InvalidCastException: [A]Engine cannot be cast to [B]Engine. Type A originates from 'MVP.Model, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'LoadNeither' at location '[...]\AppData\Roaming\Microsoft\VisualStudio\9.0\ProjectAssemblies\uankw1hh01\MVP.Model.dll'. Type B originates from 'MVP.Model, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'LoadNeither' at location '[...]\AppData\Roaming\Microsoft\VisualStudio\9.0\ProjectAssemblies\u_hge2de01\MVP.Model.dll'... So I somehow have two assemblies and they are not accessed from my project folder, but from a VS temp folder? I googled a lot and only found this: IronPython Exception: [A]Person cannot be cast to [B]Person. There is a solution offered, but first it concerns IronPhyton and second I don't know where to use it within my project? It would be just great, if u could help me out here :-) thx

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• Moq for Silverlight doesn't raise event

  - by Budda

  Trying to write Unit test for Silverlight 4.0 using Moq 4.0.10531.7 public delegate void DataReceived(ObservableCollection<TeamPlayerData> AllReadyPlayers, GetSquadDataCompletedEventArgs squadDetails); public interface ISquadModel : IModelBase { void RequestData(int matchId, int teamId); void SaveData(); event DataReceived DataReceivedEvent; } void MyTest() { Mock<ISquadModel> mockSquadModel = new Mock<ISquadModel>(); mockSquadModel.Raise(model => model.DataReceivedEvent += null, EventArgs.Empty); } Instead of raising the 'DataReceivingEvent' the following error is received: Object of type 'Castle.Proxies.ISquadModelProxy' cannot be converted to type 'System.Collections.ObjectModel.ObservableCollection`1[TeamPlayerData]'. Why attempt to convert mock to the type of 1st event parameter is performed? How can I raise an event? I've also tried another approach: mockSquadModel .Setup(model => model.RequestData(TestMatchId, TestTeamId)) .Raises(model => model.DataReceivedEvent += null, EventArgs.Empty) ; this should raise event if case somebody calls 'Setup' method... Instead the same error is generated... Any thoughts are welcome. Thanks

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• Custom Django admin URL + changelist view for custom list filter by Tags

  - by Botondus

  In django admin I wanted to set up a custom filter by tags (tags are introduced with django-tagging) I've made the ModelAdmin for this and it used to work fine, by appending custom urlconf and modifying the changelist view. It should work with URLs like: http://127.0.0.1:8000/admin/reviews/review/only-tagged-vista/ But now I get 'invalid literal for int() with base 10: 'only-tagged-vista', error which means it keeps matching the review edit page instead of the custom filter page, and I cannot figure out why since it used to work and I can't find what change might have affected this. Any help appreciated. Relevant code: class ReviewAdmin(VersionAdmin): def changelist_view(self, request, extra_context=None, **kwargs): from django.contrib.admin.views.main import ChangeList cl = ChangeList(request, self.model, list(self.list_display), self.list_display_links, self.list_filter, self.date_hierarchy, self.search_fields, self.list_select_related, self.list_per_page, self.list_editable, self) cl.formset = None if extra_context is None: extra_context = {} if kwargs.get('only_tagged'): tag = kwargs.get('tag') cl.result_list = cl.result_list.filter(tags__icontains=tag) extra_context['extra_filter'] = "Only tagged %s" % tag extra_context['cl'] = cl return super(ReviewAdmin, self).changelist_view(request, extra_context=extra_context) def get_urls(self): from django.conf.urls.defaults import patterns, url urls = super(ReviewAdmin, self).get_urls() def wrap(view): def wrapper(*args, **kwargs): return self.admin_site.admin_view(view)(*args, **kwargs) return update_wrapper(wrapper, view) info = self.model._meta.app_label, self.model._meta.module_name my_urls = patterns('', # make edit work from tagged filter list view # redirect to normal edit view url(r'^only-tagged-\w+/(?P<id>.+)/$', redirect_to, {'url': "/admin/"+self.model._meta.app_label+"/"+self.model._meta.module_name+"/%(id)s"} ), # tagged filter list view url(r'^only-tagged-(P<tag>\w+)/$', self.admin_site.admin_view(self.changelist_view), {'only_tagged':True}, name="changelist_view"), ) return my_urls + urls Edit: Original issue fixed. I now receive 'Cannot filter a query once a slice has been taken.' for line: cl.result_list = cl.result_list.filter(tags__icontains=tag) I'm not sure where this result list is sliced, before tag filter is applied. Edit2: It's because of the self.list_per_page in ChangeList declaration. However didn't find a proper solution yet. Temp fix: if kwargs.get('only_tagged'): list_per_page = 1000000 else: list_per_page = self.list_per_page cl = ChangeList(request, self.model, list(self.list_display), self.list_display_links, self.list_filter, self.date_hierarchy, self.search_fields, self.list_select_related, list_per_page, self.list_editable, self)

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• Magento install errors

  - by nXqd

  I try to install new magento version 1.4.xx . But after the config menu I meet after I copy and change local.example.xml to local.xml . Error in file: "E:\Soft\Programming\xampp\htdocs\magento\app\code\core\Mage\Catalog\sql\catalog_setup\mysql4-install-1.4.0.0.0.php" - SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '4-page_layout' for key 'entity_type_id' Trace: #0 E:\Soft\Programming\xampp\htdocs\magento\app\code\core\Mage\Core\Model\Resource\Setup.php(374): Mage::exception('Mage_Core', 'Error in file: ...') #1 E:\Soft\Programming\xampp\htdocs\magento\app\code\core\Mage\Core\Model\Resource\Setup.php(260): Mage_Core_Model_Resource_Setup->_modifyResourceDb('install', '', '1.4.0.0.21') #2 E:\Soft\Programming\xampp\htdocs\magento\app\code\core\Mage\Core\Model\Resource\Setup.php(224): Mage_Core_Model_Resource_Setup->_installResourceDb('1.4.0.0.21') #3 E:\Soft\Programming\xampp\htdocs\magento\app\code\core\Mage\Core\Model\Resource\Setup.php(153): Mage_Core_Model_Resource_Setup->applyUpdates() #4 E:\Soft\Programming\xampp\htdocs\magento\app\code\core\Mage\Core\Model\App.php(363): Mage_Core_Model_Resource_Setup::applyAllUpdates() #5 E:\Soft\Programming\xampp\htdocs\magento\app\code\core\Mage\Core\Model\App.php(295): Mage_Core_Model_App->_initModules() #6 E:\Soft\Programming\xampp\htdocs\magento\app\Mage.php(596): Mage_Core_Model_App->run(Array) #7 E:\Soft\Programming\xampp\htdocs\magento\index.php(78): Mage::run('', 'store') #8 {main} I really need your help , thanks so much :)

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• Optimized Publish/Subcribe JMS Broker Cluster and Conflicting Posts on StackOverFlow for the Answer

  - by Gene

  Hi, I am looking to build a publish/subscribe distributed messaging framework that can manage huge volumes of message traffic with some intelligence at the broker level. I don't know if there's a topology that describes this, but this is the model I'm going after: EXAMPLE MODEL A A) There are two running message brokers (ideally all on localhost if possible, for easier demo-ing) : Broker-A Broker-B B) Each broker will have 2 listeners and 1 publisher. Example Figure [subscriber A1, subscriber A2, publisher A1] <-- BrokerA <-- BrokerB <-- [publisher B1, subscriber B1, subscriber B2] IF a message-X is published to broker A and there no subscribers for it among the listeners on Broker-B (via criteria in Message Selectors or Broker routing rules), then that message-X will never be published to Broker-B. ELSE, broker A will publish the message to broker B, where one of the broker B listeners/subscribers/services is expecting that message based on the subscription criteria. Is Clustering the Correct Approach? At first, I concluded that the "Broker Clustering" concept is what I needed to support this. However, as I have come to understand it, the typical use of clustering entails either: message redundancy across all brokers ... or Competing Consumers pattern ... and neither of these satisfy the requirement in the EXAMPLE MODEL A. What is the Correct Approach? My question is, does anyone know of a JMS implementation that supports the model I described? I scanned through all the stackoverflow post titles for the search: JMS and Cluster. I found these two informative, but seemingly conflicting posts: Says the EXAMPLE MODEL A is/should-be implicitly supported: http://stackoverflow.com/questions/2255816/jms-consumer-with-activemq-network-of-brokers " this means you pick a broker, connect to it, and let the broker network sort it out amongst themselves. In theory." Says the EXAMPLE MODEL A IS NOT suported: http://stackoverflow.com/questions/2017520/how-does-a-jms-topic-subscriber-in-a-clustered-application-server-recieve-message "All the instances of PropertiesSubscriber running on different app servers WILL get that message." Any suggestions would be greatly appreciated. Thanks very much for reading my post, Gene

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• JAXB - Beans to XSD or XSD to beans?

  - by bajafresh4life

  I have an existing data model. I would like to express this data model in terms of XML. It looks like I have two options if I'm to use JAXB: Create an XSD that mirrors my data model, and use xjc to create binding objects. Marshalling and unmarshalling will involve creating a "mapping" class that would take my existing data objects and map them to the objects that xjc created. For example, in my data model I have a Doc class, and JAXB would create another Doc class with basically the same exact fields, and I would have to map from my Doc class to xjc's Doc class. Annotate my existing data model with JAXB annotations, and use schemagen to generate an XSD from my annotated classes. I can see advantanges and disadvantages of both approaches. It seems that most people using JAXB start with the XSD file. It makes sense that the XSD should be the gold standard truth, since it expresses the data model in a truly cross-platform way. I'm inclined to start with the XSD first, but it seems icky that I have to write and maintain a separate mapping class that shuttles data in between my world and JAXB world. Any recommendations?

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• Should I have different models and views for no user data than for some user data?

  - by Sam Holder

  I'm just starting to learn asp.net mvc and I'm not sure what the right thing to do is. I have a user and a user has a collection of (0 or more) reminders. I have a controller for the user which gets the reminders for the currently logged in user from a reminder service. It populates a model which holds some information about the user and the collection of reminders. My question is should I have 2 different views, one for when there are no reminders and one for when there are some reminders? Or should I have 1 view which checks the number of reminders and displays different things? Having one view seems wrong as then I end up with code in my view which says if (Model.Reminders.Count==0){//do something} else {do something else}, and having logic in the view feels wrong. But if I want to have 2 different views then I'd like to have some code like this in my controller: [Authorize] public ActionResult Index() { MembershipUser currentUser = m_membershipService.GetUser(); IList<Reminder> reminders = m_reminderRepository.GetReminders(currentUser); if (reminders.Count == 0) { var model = new EmptyReminderModel { Email = currentUser.Email, UserName = currentUser.UserName }; return View(model); } else { var model = new ReminderModel { Email = currentUser.Email, UserName = currentUser.UserName, Reminders = reminders }; return View(model); } but obviously this doesn't compile as the View can't take both different types. So if I'm going to do this should I return a specific named view from my controller, depending on the emptiness of the reminders, or should my Index() method redirect to other actions like so: [Authorize] public ActionResult Index() { MembershipUser currentUser = m_membershipService.GetUser(); IList<Reminder> reminders = m_reminderRepository.GetReminders(currentUser); if (reminders.Count == 0) { return RedirectToAction("ShowEmptyReminders"); } else { return RedirectToAction("ShowReminders"); } } which seems nicer but then I need to re-query the reminders for the current user in the ShowReminders action. Or should I be doing something else entirely?

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• Django's post_save signal behaves weirdly with models using multi-table inheritance

  - by hekevintran

  Django's post_save signal behaves weirdly with models using multi-table inheritance I am noticing an odd behavior in the way Django's post_save signal works when using a model that has multi-table inheritance. I have these two models: class Animal(models.Model): category = models.CharField(max_length=20) class Dog(Animal): color = models.CharField(max_length=10) I have a post save callback called echo_category: def echo_category(sender, **kwargs): print "category: '%s'" % kwargs['instance'].category post_save.connect(echo_category, sender=Dog) I have this fixture: [ { "pk": 1, "model": "animal.animal", "fields": { "category": "omnivore" } }, { "pk": 1, "model": "animal.dog", "fields": { "color": "brown" } } ] In every part of the program except for in the post_save callback the following is true: from animal.models import Dog Dog.objects.get(pk=1).category == u'omnivore' # True When I run syncdb and the fixture is installed, the echo_category function is run. The output from syncdb is: $ python manage.py syncdb --noinput Installing json fixture 'initial_data' from '~/my_proj/animal/fixtures'. category: '' Installed 2 object(s) from 1 fixture(s) The weird thing here is that the dog object's category attribute is an empty string. Why is it not 'omnivore' like it is everywhere else? As a temporary (hopefully) workaround I reload the object from the database in the post_save callback: def echo_category(sender, **kwargs): instance = kwargs['instance'] instance = sender.objects.get(pk=instance.pk) print "category: '%s'" % instance.category post_save.connect(echo_category, sender=Dog) This works but it is not something I like because I must remember to do it when the model inherits from another model and it must hit the database again. The other weird thing is that I must do instance.pk to get the primary key. The normal 'id' attribute does not work (I cannot use instance.id). I do not know why this is. Maybe this is related to the reason why the category attribute is not doing the right thing?

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• Syncing data between devel/live databases in Django

  - by T. Stone

  With Django's new multi-db functionality in the development version, I've been trying to work on creating a management command that let's me synchronize the data from the live site down to a developer machine for extended testing. (Having actual data, particularly user-entered data, allows me to test a broader range of inputs.) Right now I've got a "mostly" working command. It can sync "simple" model data but the problem I'm having is that it ignores ManyToMany fields which I don't see any reason for it do so. Anyone have any ideas of either how to fix that or a better want to handle this? Should I be exporting that first query to a fixture first and then re-importing it? from django.core.management.base import LabelCommand from django.db.utils import IntegrityError from django.db import models from django.conf import settings LIVE_DATABASE_KEY = 'live' class Command(LabelCommand): help = ("Synchronizes the data between the local machine and the live server") args = "APP_NAME" label = 'application name' requires_model_validation = False can_import_settings = True def handle_label(self, label, **options): # Make sure we're running the command on a developer machine and that we've got the right settings db_settings = getattr(settings, 'DATABASES', {}) if not LIVE_DATABASE_KEY in db_settings: print 'Could not find "%s" in database settings.' % LIVE_DATABASE_KEY return if db_settings.get('default') == db_settings.get(LIVE_DATABASE_KEY): print 'Data cannot synchronize with self. This command must be run on a non-production server.' return # Fetch all models for the given app try: app = models.get_app(label) app_models = models.get_models(app) except: print "The app '%s' could not be found or models could not be loaded for it." % label for model in app_models: print 'Syncing %s.%s ...' % (model._meta.app_label, model._meta.object_name) # Query each model from the live site qs = model.objects.all().using(LIVE_DATABASE_KEY) # ...and save it to the local database for record in qs: try: record.save(using='default') except IntegrityError: # Skip as the record probably already exists pass

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• getting proxies of the correct type in nhibernate

  - by Nir

  I have a problem with uninitialized proxies in nhibernate The Domain Model Let's say I have two parallel class hierarchies: Animal, Dog, Cat and AnimalOwner, DogOwner, CatOwner where Dog and Cat both inherit from Animal and DogOwner and CatOwner both inherit from AnimalOwner. AnimalOwner has a reference of type Animal called OwnedAnimal. Here are the classes in the example: public abstract class Animal { // some properties } public class Dog : Animal { // some more properties } public class Cat : Animal { // some more properties } public class AnimalOwner { public virtual Animal OwnedAnimal {get;set;} // more properties... } public class DogOwner : AnimalOwner { // even more properties } public class CatOwner : AnimalOwner { // even more properties } The classes have proper nhibernate mapping, all properties are persistent and everything that can be lazy loaded is lazy loaded. The application business logic only let you to set a Dog in a DogOwner and a Cat in a CatOwner. The Problem I have code like this: public void ProcessDogOwner(DogOwner owner) { Dog dog = (Dog)owner.OwnedAnimal; .... } This method can be called by many diffrent methods, in most cases the dog is already in memory and everything is ok, but rarely the dog isn't already in memory - in this case I get an nhibernate "uninitialized proxy" but the cast throws an exception because nhibernate genrates a proxy for Animal and not for Dog. I understand that this is how nhibernate works, but I need to know the type without loading the object - or, more correctly I need the uninitialized proxy to be a proxy of Cat or Dog and not a proxy of Animal. Constraints I can't change the domain model, the model is handed to me by another department, I tried to get them to change the model and failed. The actual model is much more complicated then the example and the classes have many references between them, using eager loading or adding joins to the queries is out of the question for performance reasons. I have full control of the source code, the hbm mapping and the database schema and I can change them any way I want (as long as I don't change the relationships between the model classes). I have many methods like the one in the example and I don't want to modify all of them. Thanks, Nir

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