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• Product table, many kinds of product, each product has many parameters

  - by StoneHeart

  Hi, i'm have not much experience in table design. My goal is a product table(s), it must design to fix some requirement below: Support many kind of products (TV, Phone, PC, ...). Each kind of product has different set of parameters like: Phone will have Color, Size, Weight, OS... PC will have CPU, HDD, RAM... Set of parameters must be dynamic. You can add or edit any parameter you like. I don't want make a table for each kind of product. So I need help to find a correct solution. Thanks.

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• Singleton: How should it be used

  - by Loki Astari

  Edit: From another question I provided an answer that has links to a lot of questions/answers about singeltons: More info about singletons here: So I have read the thread Singletons: good design or a crutch? And the argument still rages. I see Singletons as a Design Pattern (good and bad). The problem with Singleton is not the Pattern but rather the users (sorry everybody). Everybody and their father thinks they can implement one correctly (and from the many interviews I have done, most people can't). Also because everybody thinks they can implement a correct Singleton they abuse the Pattern and use it in situations that are not appropriate (replacing global variables with Singletons!). So the main questions that need to be answered are: When should you use a Singleton How do you implement a Singleton correctly My hope for this article is that we can collect together in a single place (rather than having to google and search multiple sites) an authoritative source of when (and then how) to use a Singleton correctly. Also appropriate would be a list of Anti-Usages and common bad implementations explaining why they fail to work and for good implementations their weaknesses. So get the ball rolling: I will hold my hand up and say this is what I use but probably has problems. I like "Scott Myers" handling of the subject in his books "Effective C++" Good Situations to use Singletons (not many): Logging frameworks Thread recycling pools /* * C++ Singleton * Limitation: Single Threaded Design * See: http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf * For problems associated with locking in multi threaded applications * * Limitation: * If you use this Singleton (A) within a destructor of another Singleton (B) * This Singleton (A) must be fully constructed before the constructor of (B) * is called. */ class MySingleton { private: // Private Constructor MySingleton(); // Stop the compiler generating methods of copy the object MySingleton(MySingleton const& copy); // Not Implemented MySingleton& operator=(MySingleton const& copy); // Not Implemented public: static MySingleton& getInstance() { // The only instance // Guaranteed to be lazy initialized // Guaranteed that it will be destroyed correctly static MySingleton instance; return instance; } }; OK. Lets get some criticism and other implementations together. :-)

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• Test assembly code on a mac

  - by happyCoding25

  Hello, A while back I was following some tutorials an assembly. I was running it all on a windows machine, compiling with NASM and then writing the compiled code to a floppy disk, then reboot and try the code. This process was long and time consuming and sadly was not on a mac. When I found out that Xcode for mac installed NASM I immediately tried to compile some code. The code compiled fine. The issue is testing it. On a mac I have no floppy (not like I want to use one) so Im not sure how to test this. I looked in to Q (kju) and found it would only emulate things on an ISO file. So I guess what Im asking is is it possible to install the compiled code on an ISO file for testing? (Note: the code when compiled forms a .bin file) Thanks for any help

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• Using Agile development when building websites

  - by Sam

  Is it possible / plausible to apply Agile development to the website building process including planning, design and development?

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• Easiest way of unit testing C code with Python

  - by Jon Mills

  I've got a pile of C code that I'd like to unit test using Python's unittest library (in Windows), but I'm trying to work out the best way of interfacing the C code so that Python can execute it (and get the results back). Does anybody have any experience in the easiest way to do it? Some ideas include: Wrapping the code as a Python C extension using the Python API Wrap the C code using SWIG Add a DLL wrapper to the C code and load it into Python using ctypes Add a small XML-RPC server to the c-code and call it using xmlrpclib (yes, I know this seems a bit far-out!) Is there a canonical way of doing this? I'm going to be doing this quite a lot, with different C modules, so I'd like to find a way which is least effort.

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• What are the most commonly used anti-patterns?

  - by Esteban Araya

  I'm just wondering what are some of the classic mistakes we all make. I think before working on writing good code, you must learn to recognize bad code... especially when it's YOUR code!

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• where should we send notification for updating many views?

  - by Thanh-Cong Vo

  Hi all, I want to ask about software design. I have a task, the view controller handles UI event for calling a model manger to perform that task. After finishing, the model manager will callback to update the view. There have also other views who care about that task, and also want to update its own view when that task is finished. So I register a Notification for that task in each views. The problem is defining where should I send Notification, in Model manager or in the View who handles event and receives the callback from Model manager? What is better design? Shoud the model care about send this "common" task, or shoud the view? Thanks

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• Is it easy to switch from relational to non-relational databases with Rails?

  - by Tam

  Good day, I have been using Rails/Mysql for the past while but I have been hearing about Cassandra, MongoDB, CouchDB and other document-store DB/Non-relational databases. I'm planning to explore them later as they might be better alternative for scalability. I'm planning to start an application soon. Will it make a different with Rails design if I move from relational to non-relational database? I know Rails migrations are database-agnostic but wasn't sure if moving to non-relational will make difference with design or not.

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• Where can I find free WPF controls and control templates?

  - by Geoffrey Chetwood

  Duplicate: Where can I find free WPF controls and control templates? I am looking for some recommendations on good places to find libraries of controls/templates/styles for WPF. I know about the usual places like Infragistics, but it seems to me that there should be some kind of community effort by now to share nice, clean, well written controls for WPF controls. I am not big on the design side, and it would be nice to fill out my personal libraries with some nice examples from people who are better at design. Any ideas/recommendations?

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• redoing object model construction to fit with asynchronous data fetching

  - by Andrew Patterson

  I have a modeled a set of objects that correspond with some real world concepts. TradeDrug, GenericDrug, TradePackage, DrugForm Underlying the simple object model I am trying to provide is a complex medical terminology that uses numeric codes to represent relationships and concepts, all accessible via a REST service - I am trying to hide away some of that complexity with an object wrapper. To give a concrete example I can call TradeDrug d = Searcher.FindTradeDrug("Zoloft") or TradeDrug d = new TradeDrug(34) where 34 might be the code for Zoloft. This will consult a remote server to find out some details about Zoloft. I might then call GenericDrug generic = d.EquivalentGeneric() System.Out.WriteLine(generic.ActiveIngredient().Name) in order to get back the generic drug sertraline as an object (again via a background REST call to the remote server that has all these drug details), and then perhaps find its ingredient. This model works fine and is being used in some applications that involve data processing. Recently however I wanted to do a silverlight application that used and displayed these objects. The silverlight environment only allows asynchronous REST/web service calls. I have no problems with how to make the asychhronous calls - but I am having trouble with what the design should be for my object construction. Currently the constructors for my objects do some REST calls sychronously. public TradeDrug(int code) { form = restclient.FetchForm(code) name = restclient.FetchName(code) etc.. } If I have to use async 'events' or 'actions' in order to use the Silverlight web client (I know silverlight can be forced to be a synchronous client but I am interested in asychronous approaches), does anyone have an guidance or best practice for how to structure my objects. I can pass in an action callback to the constructor public TradeDrug(int code, Action<TradeDrug> constructCompleted) { } but this then allows the user to have a TradeDrug object instance before what I want to construct is actually finished. It also doesn't support an 'event' async pattern because the object doesn't exist to add the event to until it is constructed. Extending that approach might be a factory object that itself has an asynchronous interface to objects factory.GetTradeDrugAsync(code, completedaction) or with a GetTradeDrugCompleted event? Does anyone have any recommendations?

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• Normalize or Denormalize in high traffic websites

  - by Inam Jameel

  what is the best practice for database design for high traffic websites like this one stackoverflow? should one must use normalize database for record keeping or normalized technique or combination of both? is it sensible to design normalize database as main database for record keeping to reduce redundancy and at the same time maintain another denormalized form of database for fast searching? or main database should be denormalize and one can make normalized views in the application level for fast database operations? or beside above mentioned approach? what is the best practice of designing high traffic websites???

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• Signs to Quit Programming?

  - by acidzombie24

  I was hanging out with two people and one of them had a design book and the other was talking to me about programming and design. He said he had difficulties programming and wondered what are signs that you should not or should stop programming? He wanted to know if he should stick to design and i said i didnt know since i havent seen him do either. How does one know if he or she should quit programming and stick to another discipline? and what are some signs?

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• Do you have any tips for comments code to keep them in step with the code?

  - by Rob Wells

  G'day, I've read both of Steve McConnell's excellent Code Complete books "Code Complete" and "Code Complete 2" and was wondering if people have any other suggestions for commenting code. My commenting mantra could be summed up by the basic idea of expressing "what the code below cannot say". While enjoying this interesting blog post by Jeff about commenting I was still left wondering "When coding, when do you feel a comment is required?" Edit: Oops. Seems to be a duplicate of this question http://stackoverflow.com/questions/121945/how-do-you-like-your-comments so sorry for the noise. Thanks to my, seemingly, SO shadow for pointing it out - wouldn't have thought I was that interesting. Now off to read the original post and see if it is relevant. Edit: I meant to emphasise the best appraoch to ensure that your comments will stay in step with the code. Maybe expressing an intent rather than the mechansim for instance.

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• Best way to fetch data from a single database table with multiple threads?

  - by Ravi Bhatt

  Hi, we have a system where we collect data every second on user activity on multiple web sites. we dump that data into a database X (say MS SQL Server). we now need to fetch data from this single table from daatbase X and insert into database Y (say mySql). we want to fetch time based data from database X through multiple threads so that we fetch as fast as we can. Once fetched and stored in database Y, we will delete data from database X. Are there any best practices on this sort of design? any specific things to take care on table design like sharing or something? Are there any other things that we need to take care to make sure we fetch it as fast as we can from threads running on multiple machines? Thanks in advance! Ravi

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• seeing C# windows forms project code from F#

  - by Pessimist

  I have a C# Windows Forms project open with some C# code in it. Question: How can I have an F# file that I can write F# code in but still referencing all the C# code I have on Form1.cs (including the GUI). I can successfully do this: - Create a C# Windows Forms project - Create a F# Library project - Reference the F# Library DLL from my C# project - That way I can call F# functions from C# But I still can't see my buttons and textboxes from F# I understand that that is because it's a library and it can't reference System.Windows.Forms So how do I fix this? I don't want it to be a library or this or that, I just want it to be a file that will allow me to write F# code while being able to reference my C# Form and code. I guess you can say I want an F# file that is also a "partial class Form1" so that I can continue writing code for the same Project, but using F# instead. How do I do that?

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• How are SaaS applications organized?

  - by tomekw

  Consider web (MVC, for example Rails) application for multiple clients as a service. How to design this? one application instance per client? (+ one database per client) one instance for all clients (+ one database for all clients) Former one is simple, but... "inefficient". How about the latter? (best practises, design patterns) How to separate client data? For example: worker "A" of client "1" has two documents, worker "B" of client "2" has three documents. How to build model associations to protect other users (and clients) data? I think joining every query with Client model is not a good solution.

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• When is referential integrity not appropriate?

  - by Curtis Inderwiesche

  I understand the need to have referential integrity for limiting specific values on entry or possibly preventing them from removal upon a request of deletion. However, I am unclear as to a valid use case which would exclude this mechanism from always being used. I guess this would fall into several sub-questions: When is referential integrity not appropriate? Is it appropriate to have fields containing multiple and/or possibly incomplete subsets of a foreign key's list? Typically, should this be a schema structure design decision or an interface design decision? (Or possibly neither or both) Thoughts?

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• A way to avoid deriving from the provider classes in mvc authentication

  - by Shymep

  Looking for the best practice for authentication in MVC I unfortunately didn't find the clear answer to my question. Thinking of the problem I tried to imagine some priciples that could be useful in my design. Well, I would like to use a base AccountController class I want to place all the tables such as "Users", Roles, Rights etc into my own database. But I wouldn't like to implement the standard aspnetdb design (which can be easy got by using aspnet_regsql) So the main question is can I do this without deriving abstract classes like MembershipProvider, RoleProvider etc? What I would prefer not to do is implement all the abstract methods from these classes. The second question is still about the best practice for authentication e.g. for the small projects, for the large ones?

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• What is the point in using a "real" database modeling tool?

  - by cdeszaq

  We currently have a 10 year old nasty, spaghetti-code-style SQL Server database that we are soon looking to pretty much re-write from scratch as part of a re-write to a large web application. (The existing application will serve as the functional requirements for the next incarnation of the app). Some have suggested we use Visio to do all the diagramming and to generate the DDL, but others have suggested we use a dedicated database design tool, rather than a diagramming tool that is able to export DDL. Is there any benefit to using "real" DB design tools, such as ModelRight, over general tools like Visio? If so, what are those specific benefits? Edit: In a nutshell, what can real/dedicated tools do that something like Visio can't, and how much do these capabilities matter (from a best-practices standpoint, for example)

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• Advice on software / database design to avoid using cursors when updating database

  - by Remnant

  I have a database that logs when an employee has attended a course and when they are next due to attend the course (courses tend to be annual). As an example, the following employee attended course '1' on 1st Jan 2010 and, as the course is annual, is due to attend next on the 1st Jan 2011. As today is 20th May 2010 the course status reads as 'Complete' i.e. they have done the course and do not need to do it again until next year: EmployeeID CourseID AttendanceDate DueDate Status 123456 1 01/01/2010 01/01/2011 Complete In terms of the DueDate I calculate this in SQL when I update the employee's record e.g. DueDate = AttendanceDate + CourseFrequency (I pull course frequency this from a separate table). In my web based app (asp.net mvc) I pull back this data for all employees and display it in a grid like format for HR managers to review. This allows HR to work out who needs to go on courses. The issue I have is as follows. Taking the example above, suppose today is 2nd Jan 2011. In this case, employee 123456 is now overdue for the course and I would like to set the Status to Incomplete so that the HR manager can see that they need to action this i.e. get employee on the course. I could build a trigger in the database to run overnight to update the Status field for all employees based on the current date. From what I have read I would need to use cursors to loop over each row to amend the status and this is considered bad practice / inefficient or at least something to avoid if you can??? Alternatively, I could compute the Status in my C# code after I have pulled back the data from the database and before I display it on screen. The issue with this is that the Status in the database would not necessarily match what is shown on screen which just feels plain wrong to me. Does anybody have any advice on the best practice approach to such an issue? It helps, if I did use a cursor I doubt I would be looping over more than 1000 records at any given time. Maybe this is such small volume that using cursors is okay?

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• how to profile my code??

  - by kaki

  i want to how to profile my code... i have gone through the docs , but as there were no example codes given i could not get anything from it. i have a large code and it is taking so much time hence want to profile and increase its speed. i havent written my code in method , there are few in between but not completely. i dont have any main in my code..i want to know how to use profiling.. looking for some example or sample code of about how to profile.. i tried psyco i.e just addded two line at the top of my code import psyco psyco.full() is this write,it did not show any improvement. and other way of speeding up ,please suggest. thanks in advance..

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• How's my pygame code?

  - by Isaiah

  I'm still getting the hang of lots of things and thought I should post some code I made with pygame and get some feedback^^. I posted code here: http://urlvars.com/code/snippet/39272/my-bouncing-program http://urlvars.com/code/snippet/39273/my-bouncing-program-classes There's tome things that I implemented that I'm not using yet I just realized like a timer at the bottom of the main while loop. If my code isn't readable, I'm sorry, I'm self taught and this is the first code I've ever posted anywhere. By the way I made some variables that take the screensize and half it to find a point to spit out the squares, but when I try to use it, it makes a weird effect :/ Try switching the list i have in the newbyte() function with the halfScreen variable and see it freak out o.O thank you

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• Storing Templates and Object-Oriented vs Relational Databases

  - by syrion

  I'm designing some custom blog software, and have run into a conundrum regarding database design. The software requires that there be multiple content types, each of which will require different entry forms and presentation templates. My initial instinct is to create these content types as objects, then serialize them and store them in the database as JSON or YAML, with the entry forms and templates as simple strings attached to the "contentTypes" table. This seems cumbersome, however. Are there established best practices for dealing with this design? Is this a use case where I should consider an object database? If I should be using an object database, which should I consider? I am currently working in Python and would prefer a capable Python library, but can move to Java if need be.

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• Code completion in NetBeans' python plugin does not work properly

  - by T.K.

  I am asking on StackOverflow because surely I am doing something completely silly and I hope S.O. might provide me with a quick answer. I've installed the latest stable Python-plugin for NetBeans. It works great, and I tested code completion with various packages such as sys, os and so on. It works beautifully. However, it does not seem to pick up the code completion for the code in my own project. I created a package called mypackage (it has _init_.py as well), and in it I have a module called mymodule.py. Inside mymodule I've put a class called MyClass, complete with doc-strings and all. Please refer to this screenshot to describe what happens in code-completion: As you see, it's suggesting irrelevant things, as opposed to just MyClass. (Note that if I execute mymodule.MyClass() it works 100%, it's just that I would really like code completion on my own code) Hope I'm just doing something silly here... Any ideas?

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• Designing a Tag table that tells how many times it's used

  - by Satoru.Logic

  Hi, all. I am trying to design a tagging system with a model like this: Tag: content = CharField creator = ForeignKey used = IntergerField It is a many-to-many relationship between tags and what's been tagged. Everytime I insert a record into the assotication table, Tag.used is incremented by one, and decremented by one in case of deletion. Tag.used is maintained because I want to speed up answering the question 'How many times this tag is used?'. However, this seems to slow insertion down obviously. Please tell me how to improve this design. Thanks in advance.

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