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• ASP.net Error in Design Mode

  - by stringo0

  I just switched to VS 2010, and upgraded a previous project. I'm getting the following error on a page in design mode for 2 controls: Error Creating Control - ObjectName Object reference not set to an instance of an object. One of them is a simple label, and the other is a ajax update panel. Other pages look fine. When I build and test the app, the page renders fine in the browser and functions fine - the label functions as expected and the content in the update panel works as expected. Any ideas why I'm getting this error? I tried some of the google results to no avail. It'd be great to get this out of the way. Thanks!

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• Best Design for a Facebook clone on GAE Java

  - by charming30

  My current App is written in Python on GAE which can do Contacts management, Genealogy, Social Networking, Photo sharing, Telecom Integration (SMS, iVRS, URL Billing), CRON and performs business logic operations for our Mobile Apps. Current Architecture indlues python, django, jquery, memcache and few telecom APIs. Now, It feels that an SOA Architecture on GAE using Java would be really ideal and scalable for this kind of App where we want to build new features like widgets that users can turn on or off and third party developers can also develop and deploy features. Please correct me or improve the following design decision: UI (Current plan is GWT) Sessions, Security and ACL (Spring MVC 2.x) Reusable Business Logic components (?) Implementation of Web Services (?) Your advice would really help.

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• Advantage of using a static member function instead of an equivalent non-static member function?

  - by jonathanasdf

  I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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• Ooutsourcing design/programming (taxes!)

  - by alexeypro

  Hello, I have a full time job, but I also have some ideas in mind -- and I want to outsource some code development and design to Russia. I have friends there who help me to do that -- they'll do the development, provide me invoice (which is just description of our terms, because we decided on flat rate monthly fee), and I need to wire them money. So, I do not have business entity. If I'll pay them, am I am required to pay taxes? Or do I deduct my business expenses (say $30K/year) from my earnings (say $50K/year), and pay taxes only on what's left ($20K to be precise)? Any rules on that? Am I limited with something here? Thanks!

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• Specification Pattern vs Spec in BDD

  - by cadmium

  I'm trying to explore Behavior Driven Design and Domain Driven Design. I'm getting that written specifications drive the tests in BDD, but also that business logic can be encapsulated using the specification pattern for re-use in domain objects and repositories, etc. Are these basically the same concept just used in different ways, used in conjunction together, or am I completely confusing the concepts? Please shed some light, if possible.

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• Proper way to set object instance variables

  - by ensnare

  I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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• 2D World design question

  - by Maciek

  I'm facing a problem which is probably extremely common in game-design. Let's assume that we've got a 2D world The world's size is M x N rect The world may contain some items in it The items have (x,y) coords The world can be browsed via a window that is physically (m x n) large. The browser window can be zoomed in / out The browser window can be panned up/down + left right, while in the extents of the world's rect. How should I go about implementing this? I'm especially concerned about the browser window. Can anyone recommend any good reads ? This is not a homework - it's more of a task which I've set myself to complete.

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• Model-Controller cyclic reference/design problem

  - by jasamer

  I have a CoreData entity X, and controllers for this entity, XController. Now there's another entity, XGroup, containing a collection of X entities, and a XGroupController. Now the problem is that XGroupController needs to interact with XController, and it would be nice to just pass XGroupController a XGroup to observe, and then get the XControllers from the X entities. So the question is: is it a good idea to store a (weak, to avoid retain cycles) reference to a controller in an entity? It just feels a bit "wrong". Is there another design pattern for this?

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• Observer pattern used with decorator pattern

  - by icelated

  I want to make a program that does an order entry system for beverages. ( i will probably do description, cost) I want to use the Decorator pattern and the observer pattern. I made a UML drawing and saved it as a pic for easy viewing. This site wont let me upload as a word doc so i have to upload a pic - i hope its easily viewable.... I need to know if i am doing the UML / design patterns correctly before moving on to the coding part. Beverage is my abstract component class. Espresso, houseblend, darkroast are my concrete subject classes.. I also have a condiment decorator class milk,mocha,soy,whip. would be my observer? because they would be interested in data changes to cost? Now, would the espresso,houseblend etc, be my SUBJECT and the condiments be my observer? My theory is that Cost is a changes and that the condiments need to know the changes? So, subject = esspresso,houseblend,darkroast,etc.. // they hold cost() Observer = milk,mocha,soy,whip? // they hold cost() would be the concrete components and the milk,mocha,soy,whip? would be the decorator! So, following good software engineering practices "design to an interface and not implementation" or "identify things that change from those that dont" would i need a costbehavior interface? If you look at the UML you will see where i am going with this and see if i am implementing observer + Decorator pattern correctly? I think the decorator is correct. since, the pic is not very viewable i will detail the classes here: Beverage class(register observer, remove observer, notify observer, description) these classes are the concrete beverage classes espresso, houseblend,darkroast, decaf(cost,getdescription,setcost,costchanged) interface observer class(update) // cost? interface costbehavior class(cost) // since this changes? condiment decorator class( getdescription) concrete classes that are linked to the 2 interface s and decorator are: milk,mocha,soy,whip(cost,getdescription,update) these are my decorator/ wrapper classes. Thank you.. Is there a way to make this picture bigger?

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• Two objects with dependencies for each other. Is that bad?

  - by Kasper Grubbe

  Hi SO. I am learning a lot about design patterns these days. And I want to ask you about a design question that I can't find an answer to. Currently I am building a little Chat-server using sockets, with multiple Clients. Currently I have three classes. Person-class which holds information like nick, age and a Room-object. Room-class which holds information like room-name, topic and a list of Persons currently in that room. Hotel-class which have a list of Persons and a list of Rooms on the server. I have made a diagram to illustrate it (Sorry for the big size!): http://i.imgur.com/Kpq6V.png I have a list of players on the server in the Hotel-class because it would be nice to keep track of how many there are online right now (Without having to iterate through all of the rooms). The persons live in the Hotel-class because I would like to be able to search for a specific Person without searching the rooms. Is this bad design? Is there another way of achieve it? Thanks.

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• Practically expected transfer rates for sdhc class 6

  - by bobobobo

  I went and bought an expensive SanDisk Extreme III SDHC 8GB class 6 chip. However when I dump data from the card to the machine via USB 2.0 cable, its only getting 5.0 MB/second maximum according to Windows 7 disk explorer. It still can take up to 20 minutes to dump the card when its near full. This is so far below the rated 20MB/s transfer speed I can't believe it. Is this normal or might I have a defective chip?

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• Reference for good Android UI design patterns.

  - by sat

  Hi, I would like to get some links for getting started with design patterns.My requirement is , (at Initial stage) How to go about developing a particular pattern , say customized ListView which can be shared across applications . e.g. Applications will call something like drawCustomizedListView(params...) and my code will draw the listview according to the parameters supplied. This is particularly useful when across the applications I have to draw customized views. My intention is, I should not repeat the same code everywhere for doing similar task. Any references for the above requirement ?

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• design time usercontrols - I can't see anything!

  - by taglius

  newbie question, please forgive... I'm developing a Wpf UserControl that will eventually be bound to a business object. The usercontrol is little more than a series of laid out TextBlocks, and perhaps (later) an image or two. As I'm laying out the usercontrol, I can put dummy text into all the TextBlocks so I can see what the usercontrol will look like, but as soon as I change the text property to contain the Binding information: <TextBlock Margin="0,12.8,42,0" Name="lblLastName" FontSize="8" Height="19" VerticalAlignment="Top" Text="{Binding Mode=OneWay, Path=LastName}"/> Then I can no longer see the textbox, or any "placeholder" text. This makes it very difficult to adjust the location and sizes of all the controls on the UserControl. In WinFormas programming, you could set binding information independently of the Text property, so you could at least see the Placeholder text during design time development. It's going to be pretty hard to visually arrange a bunch of invisible TextBlocks! What's the standard solution for this?

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• ASP.NET Custom Control

  - by Alyn

  I am building an ASP.NET Web User Control which has a panel within it. How do I make the Panel within the user control resizable (i.e. with handles) at design time in Visual Studio. I need to create a design class or something?? Thanks.

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• Form Design ScriptControlClass

  - by raghumithra

  I am working on a form designer. We have two parts: first is designing form by placing controls, and second is writing VB code in rich text editor. How do i integrate design and code (events of the controls) in runtime? I am using ScriptControlClass Form4 f4 = new Form4(); f4.Name = "dgfdfg"; f4.Text = "Raghudfgmithra"; Button btn = new Button(); btn.Text = "HI"; btn.Left = 25; btn.Top = 50; btn.Name = "btnSubmit"; f4.Controls.Add(btn); script.AddObject("form", f4, true); script.AddCode("???????????); script.ExecuteStatement(????????????);

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• CodeIgniter based e-shop, shipping and gift address design problem

  - by alexander

  While building an ecommerce platform I have run into design problems. I'm working with the built-in CodeIgniter's cart class. It stores all the cart information in session. Let say that cart has already been filled with products and user clicks checkout. When should I store order in database? Just after that click or after several steps of gathering information and stoing it in session? How to deal with additional features like different shipping methods? Should I add it to the basket first and get additional (gift address) to session? I dont want to store it in database because of the relation between gift address and order is needed and since I dont know what's the ID of the order. I'm puzzled :) Additionally I think its crucial to keep cart aware of shipping methods and additional bought services (by selecting gift address there is an extra fee) because the cart content is just like an reciept? In brief, what is the best practice to process checkout?

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• SOA design principles with regards to database relationships

  - by Eitan

  If I were to extricate my current membership provider from my solution, i.e. as a dll and expose it as a web service with it's own db, how would I model the relationships with regards to SOA design. For example I have a table: USER id, name, lastname, username, password, role. and table PRODUCT id, name, price, createdate, userid the foreign key being userid to table user. How would I model the relationship and/or query the db. If I wanted to get all products that were uploaded today for example, before I would query: SELECT u.name, u.lastname, u.username, p.* FROM PRODUCT p INNER JOIN USER u ON p.userid = u.id WHERE createdate = '05/05/2010' Now that I don't have the table within the database how would I perform this query? Thanks.

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• Fixed footer with 960.gs

  - by Oguz

  I want to create fixed footer but , is it possible with 960 gs , because I am having trouble with height of container div . I can no set it to %100. <div class="container_12" > <div class="grid_3" id="side-space"></div> <div class="grid_6"> <div id="content-box"></div> </div> <div class="grid_3" id="side-space"></div> </div>

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• Best design for generating code from an AST?

  - by Sam Washburn

  I'm working on a pretty complex DSL that I want to compile down into a few high level languages. The whole process has been a learning experience. The compiler is written in java. I was wondering if anyone knew a best practice for the design of the code generator portion. I currently have everything parsed into an abstract syntax tree. I was thinking of using a template system, but I haven't researched that direction too far yet as I would like to hear some wisdom first from stack overflow. Thanks!

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• Is a "factory" method the right pattern?

  - by jdt141

  Hey all - So I'm working to improve an existing implementation. I have a number of polymorphic classes that are all composed into a higher level container class. The problem I'm dealing with at the moment is that the higher level container class, well, sucks. It looks something like this, which I really don't have a problem with (as the polymorphic classes in the container should be public). My real issue is the constructor... /* * class1 and class 2 derive from the same superclass */ class Container { public: boost::shared_ptr<ComposedClass1> class1; boost::shared_ptr<ComposedClass2> class2; private: ... } /* * Constructor - builds the objects that we need in this container. */ Container::Container(some params) { class1.reset(new ComposedClass1(...)); class2.reset(new ComposedClass2(...)); } What I really need is to make this container class more re-usable. By hard-coding up the member objects and instantiating them, it basically isn't and can only be used once. A factory is one way to build what I need (potentially by supplying a list of objects and their specific types to be created?) Other ways to get around this problem? Seems like someone should have solved it before... Thanks!

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• Error Messaged and Error Code design

  - by Ved

  We are designing set of web services which will return XML string in response. These are RESTFul services so I will have to send exception inside element. I am planing to design set of Error code which can help me determine where level occured just by looking at the code. For Example 1000 - Application Level 2000 - DB level 3000 - Network level so if I have error message then I can know right away that this was an application level error and it came from 1st business module. I am not very experience in this so I would love to here your thoughts and criticism. Thanks

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• How do I design a cryptographic hash function?

  - by Eyal

  After reading the following about why one-way hash functions are one-way, I would like to know how to design a hash function. http://stackoverflow.com/questions/1038307/help-me-better-understand-cryptographic-hash-functions/1047106#1047106 Before everyone gets on my case: Yes, I know that it's a bad idea to not use a proven and tested hash function. I would still like to know how it's done. I'm familiar with Feistel-network ciphers but those are necessarily reversible, horrible for a cryptographic hash. Is there some sort of construction that is well-used in cryptographic hashing? Something that makes it very one-way?

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• Singleton Properties

  - by coffeeaddict

  Ok, if I create a singleton class and expose the singleton object through a public static property...I understand that. But my singleton class has other properties in it. Should those be static? Should those also be private? I just want to be able to access all properties of my singleton class by doing this: MySingletonClass.SingletonProperty.SomeProperty2 Where SingletonProperty returns me the single singleton instance. I guess my question is, how do you expose the other properties in the singleton class..make them private and then access them through your public singleton static property?

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• [C++]Advantage of using a static member function instead of an equivalent non-static member function

  - by jonathanasdf

  I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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• Future proof Primary Key design in postgresql

  - by John P

  I've always used either auto_generated or Sequences in the past for my primary keys. With the current system I'm working on there is the possibility of having to eventually partition the data which has never been a requirement in the past. Knowing that I may need to partition the data in the future, is there any advantage of using UUIDs for PKs instead of the database's built-in sequences? If so, is there a design pattern that can safely generate relatively short keys (say 6 characters instead of the usual long one e6709870-5cbc-11df-a08a-0800200c9a66)? 36^6 keys per-table is more than sufficient for any table I could imagine. I will be using the keys in URLs so conciseness is important.

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