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  • Which design pattern is most appropriate?

    - by Anon
    Hello, I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?. Here is an example (for simplicity, let's say there are only two possible algorithms) ... class Foo { private: // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1); AlgorithmInterface* a; }; class AlgorithmInterface { public: virtual void DoSomething = 0; }; class Algorithm1 : public AlgorithmInterface { public: Algorithm1( int i ) : value(i) {} virtual void DoSomething(){ // Does something with int value }; int value; }; class Algorithm2 : public AlgorithmInterface { public: Algorithm2( bool b ) : value(b) {} virtual void DoSomething(){ // Do something with bool value }; bool value; };

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  • Proper way of naming your Java Google App Engine Project

    - by Saif Bechan
    I am starting out with Google's App Engine in Java. I have seen the tutorial video but I do not understand the naming of the project package. It is going to be a guestbook, that's why the name is guestbook, I understand that part. But after that I see package name. 1)Is that something you import into the project, or is is something you create. I have seen this a lot in projects, something like com.xxx.xxx. 2)How do you name this type of thing or is this an import. I have looked at another tutorial there they take the naming to a whole new level. The name of both the project and the package is de.vogella.gae.java.todo. 3)What does this mean in java terms. 4)Maybe one of you can help me with this specific project I want to start. I want to create a Google App project that for now only serves static files. I will leave the project empty and just put all my static files in the war directory of the project. I want the domain name to be mydomainstatic

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  • What is the best way to manage application screens in SWT?

    - by parxier
    I'm creating a standalone SWT desktop application that has around 10 different screens (few wizards, help, forms, etc). Some elements on screen don't change at all (like header, background, etc) and there is a working area that changes depending on what is clicked, etc. What is the best way to manage application screens? Do I need to create all screen at startup and then show/hide them depending on what is clicked? Or do I need to create those screens dynamically? Also, I couldn't find any way to show/hide a Composite, do I need to dispose it and then create again? What is the best practice? I'm new to SWT developing outside of Eclipse so any help would be beneficial.

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  • Including partial views when applying the Mode-View-ViewModel design pattern

    - by Filip Ekberg
    Consider that I have an application that just handles Messages and Users I want my Window to have a common Menu and an area where the current View is displayed. I can only work with either Messages or Users so I cannot work simultaniously with both Views. Therefore I have the following Controls MessageView.xaml UserView.xaml Just to make it a bit easier, both the Message Model and the User Model looks like this: Name Description Now, I have the following three ViewModels: MainWindowViewModel UsersViewModel MessagesViewModel The UsersViewModel and the MessagesViewModel both just fetch an ObserverableCollection<T> of its regarding Model which is bound in the corresponding View like this: <DataGrid ItemSource="{Binding ModelCollection}" /> The MainWindowViewModel hooks up two different Commands that have implemented ICommand that looks something like the following: public class ShowMessagesCommand : ICommand { private ViewModelBase ViewModel { get; set; } public ShowMessagesCommand (ViewModelBase viewModel) { ViewModel = viewModel; } public void Execute(object parameter) { var viewModel = new ProductsViewModel(); ViewModel.PartialViewModel = new MessageView { DataContext = viewModel }; } public bool CanExecute(object parameter) { return true; } public event EventHandler CanExecuteChanged; } And there is another one a like it that will show Users. Now this introduced ViewModelBase which only holds the following: public UIElement PartialViewModel { get { return (UIElement)GetValue(PartialViewModelProperty); } set { SetValue(PartialViewModelProperty, value); } } public static readonly DependencyProperty PartialViewModelProperty = DependencyProperty.Register("PartialViewModel", typeof(UIElement), typeof(ViewModelBase), new UIPropertyMetadata(null)); This dependency property is used in the MainWindow.xaml to display the User Control dynamicly like this: <UserControl Content="{Binding PartialViewModel}" /> There are also two buttons on this Window that fires the Commands: ShowMessagesCommand ShowUsersCommand And when these are fired, the UserControl changes because PartialViewModel is a dependency property. I want to know if this is bad practice? Should I not inject the User Control like this? Is there another "better" alternative that corresponds better with the design pattern? Or is this a nice way of including partial views?

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  • MVC (model-view-controller) - can it be explained in simple terms?

    - by DVK
    I need to explain to a not-very-technical manager the MVC (model-view-controller) concept and ran into trouble. The problem is that the explanation needs to be on a "your grandma will get it" level - e.g. even the fairly straightforward explanation offered on MVC Wiki page didn't work, at least with my commentary. Does anyone have a reference to a good MVC explanation in simple terms? It would ideally be done with non-techie metaphor examples (e.g. similar to "Decorator pattern is like glasses") - one reason I failed was that all MVC examples I could come up with were development related. I once saw a list of pattern explanations but to the best of my memory MVC was not on it. Thanks!

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  • File descriptor limits and default stack sizes

    - by Charles
    Where I work we build and distribute a library and a couple complex programs built on that library. All code is written in C and is available on most 'standard' systems like Windows, Linux, Aix, Solaris, Darwin. I started in the QA department and while running tests recently I have been reminded several times that I need to remember to set the file descriptor limits and default stack sizes higher or bad things will happen. This is particularly the case with Solaris and now Darwin. Now this is very strange to me because I am a believer in 0 required environment fiddling to make a product work. So I am wondering if there are times where this sort of requirement is a necessary evil, or if we are doing something wrong. Edit: Great comments that describe the problem and a little background. However I do not believe I worded the question well enough. Currently, we require customers, and hence, us the testers, to set these limits before running our code. We do not do this programatically. And this is not a situation where they MIGHT run out, under normal load our programs WILL run out and seg fault. So rewording the question, is requiring the customer to change these ulimit values to run our software to be expected on some platforms, ie, Solaris, Aix, or are we as a company making it to difficult for these users to get going? Bounty: I added a bounty to hopefully get a little more information on what other companies are doing to manage these limits. Can you set these pragmatically? Should we? Should our programs even be hitting these limits or could this be a sign that things might be a bit messy under the covers? That is really what I want to know, as a perfectionist a seemingly dirty program really bugs me.

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  • Efficient storage/retrieval method for replayable comet style applications (Google Wave, Etherpad)

    - by Gareth Simpson
    I am considering a web application that would have the same kind of multi user, automatic saving, infinite undo / replay capabilities that you see in Google Wave and Etherpad (albeit on a drastically smaller scale and userbase). Before I go away and reinvent the wheel, is this something that has already been addressed as either a piece of technology or library, or even just a design pattern. I know this isn't necessarily the best Stack Overflow question as there is probably not a "right" answer, but my Google-fu has failed me and I'd just like a reading list! Ordinarily I would be developing under python/django but this is not a firm requirement just a preference :)

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  • Definitive method for sizing font in css

    - by David
    Hi there, I would like to know some opinions from experienced developers on what they think the definitive way to size fonts (in a base sense). I know that working with ems is considered best but im referring to the best way to set the base font size. There is the technique of setting font to 10px using 62.5 method but i think ie has an issue with rounding which throws this out slightly (perhaps not) YUI framework uses body { font:13px/1.231 arial,helvetica,clean,sans-serif; /* for IE6/7 */ *font-size:small; /* for IE Quirks Mode */ *font:x-small; } which really confuses me! Tripoli uses html { font-size:125%; } body { font-size:50%; } a list apart suggest something along the lines of : body { font-size: 16px; *font-size: 100%; } So which is the best either out of these methods or any alternatives. The best being the easiest to work with and the most reliable cross browser.

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  • How do you handle passwords or credentials for standalone applications?

    - by Abel Morelos
    Let's say that you have a standalone application (a Java application in my case) and that this application has a configuration file (a XML file in my case) where you store the credentials (user and password) for a bunch of databases you need to connect. Everything works great, but now you discover (or your are given a new requirement like me) that you have to put this application in a different server and that you can't have these credentials in the configuration files because of security and/or compliance considerations. I'm considering to use data sources hosted in the application server (a WAS server), but I think this could have poor performance and maybe it's not the best approach since I'm connecting from a standalone application. I was also considering to use some sort of encryption, but I would like to keep things as simple as possible. How would you handle this case? Where would you put these credentials or protect them from being compromised? Or how would you connect to your databases in this scenario?

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  • .NET without use of DLL's

    - by Kieran
    Hi SO community I have been issued a problem with security. A bank will not allow use of DLL's in the project. What sort of structure would be needed to allow DataAccess and or the use of external services (like an email client mailchimp, icontct). has anyone else encountered this sort of problem before? If they have how should the project be structured (.net 3.5+). Thanks, KJ

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  • Which framework exceptions should every programmer know about ?

    - by Thibault Falise
    I've recently started a new project in C#, and, as I was coding some exception throw in a function, I figured out I didn't really know which exception I should use. Here are common exceptions that are often thrown in many programs : ArgumentException ArgumentNullException InvalidOperationException Are there any framework exceptions you often use in your programs ? Which exceptions should every .net programmer know about ? When do you use custom exception ?

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  • Writing a custom iterator -- what to do if you're at the end of the array?

    - by Goose Bumper
    I'm writing a custom iterator for a Matrix class, and I want to implement the increment method, which gets called when the iterator is incremented: void MatrixIterator::increment() { // go to the next element } Suppose the iterator has been incremented too many times and now points to past the end of the matrix (i.e. past the one-past-the-end point). What is the best practice for this situation? Should I catch this with an assert, or should I just say it's the user's responsibility to keep track of where the iterator is pointing and it's none of my business?

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  • Why is debugging better in an IDE?

    - by Bill Karwin
    I've been a software developer for over twenty years, programming in C, Perl, SQL, Java, PHP, JavaScript, and recently Python. I've never had a problem I could not debug using some careful thought, and well-placed debugging print statements. I respect that many people say that my techniques are primitive, and using a real debugger in an IDE is much better. Yet from my observation, IDE users don't appear to debug faster or more successfully than I can, using my stone knives and bear skins. I'm sincerely open to learning the right tools, I've just never been shown a compelling advantage to using visual debuggers. Moreover, I have never read a tutorial or book that showed how to debug effectively using an IDE, beyond the basics of how to set breakpoints and display the contents of variables. What am I missing? What makes IDE debugging tools so much more effective than thoughtful use of diagnostic print statements? Can you suggest resources (tutorials, books, screencasts) that show the finer techniques of IDE debugging? Sweet answers! Thanks much to everyone for taking the time. Very illuminating. I voted up many, and voted none down. Some notable points: Debuggers can help me do ad hoc inspection or alteration of variables, code, or any other aspect of the runtime environment, whereas manual debugging requires me to stop, edit, and re-execute the application (possibly requiring recompilation). Debuggers can attach to a running process or use a crash dump, whereas with manual debugging, "steps to reproduce" a defect are necessary. Debuggers can display complex data structures, multi-threaded environments, or full runtime stacks easily and in a more readable manner. Debuggers offer many ways to reduce the time and repetitive work to do almost any debugging tasks. Visual debuggers and console debuggers are both useful, and have many features in common. A visual debugger integrated into an IDE also gives you convenient access to smart editing and all the other features of the IDE, in a single integrated development environment (hence the name).

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  • What XSS/CSRF attacks (if any) to be aware of when allowing video embeds?

    - by fireeyedboy
    I've been assigned a project for a website where users will be allowed to upload video's (using a YouTube API) but more importantly (for me) they will also be allowed to submit video embed codes (from numerous video sites, YouTube, Vimeo, etc. etc.). Having no experience with allowing users to embed video: How can I best protect against cross site scripting and/or cross site request forgery attacks specifically for video embedding? What are some of the common pitfalls to watch for? At a minumum I would think to strip all tags except <object> and <embed>. But I have a feeling this will not be enough, will it? If it is of importance, the environment will be: PHP/Zend Framework MySQL Bonuspoints: Is there a common minimum golden rule/code template for video embed codes that are valid across all video sites that I could use to filter the input?

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  • Python's JSON module doesn't use __get__?

    - by Matt
    When I serialize a list of objects with a custom __get__ method, __get__ is not called and the raw (unprocessed by custom __get__) value from __set__ is used. How does Python's json module iterate over an item? Note: if I iterate over the list before serializing, the correct value returned by __get__ is used.

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  • What are possible designs for the DCI architecture?

    - by Gabriel Šcerbák
    What are possibles designs for implementation of the DCI (data, contexts, interactions) architecture in different OOP languages? I thought of Policy based design (Andrei Alexandrescu) for C++, DI and AOP for Java. However, I also thought about using State design pattern for representing roles and some sort of Template method for the interactions... What are the other possibilities?

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  • c# object initializer complexity. best practice

    - by Andrew Florko
    I was too excited when object initializer appeared in C#. MyClass a = new MyClass(); a.Field1 = Value1; a.Field2 = Value2; can be rewritten shorter: MyClass a = new MyClass { Field1 = Value1, Field2 = Value2 } Object initializer code is more obvious but when properties number come to dozen and some of the assignment deals with nullable values it's hard to debug where the "null reference error" is. Studio shows the whole object initializer as error point. Nowadays I use object initializer for straightforward assignment only for error-free properties. How do you use object initializer for complex assignment or it's a bad practice to use dozen of assigments at all? Thank you in advance!

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  • How to handle management trying to interfere with the project (including architecture decision)

    - by Zwei Steinen
    I feel this is not a very good question to post on SO, but I need some advice from experienced developers... (I'm a second year developer) I guess this is a problem to many, many projects, but in our case, it is getting intense. There were so much interference from people that don't know a bit about software development, that our development came to an almost complete stop. We had to literary escape to another location to get any useful job done. Now we were happily producing results, but then I get a request for a "meeting" and it's them again. I have a friendly relationship with them, but I feel very daunted at the thought of talking about non-sense all over again. Should I be firm and tell them to shut up and wait for our results? Or should I be diplomatic and create an illusion they are making a positive contribution or something?? My current urge is to be unfriendly and murmur some stuff so they will give up or something. What would you do if you were in this situation?

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  • What performance overhead do IoC containers involve?

    - by Sosh
    Hi, Loose coupling is wonderful of course, but I have often wondered what overhead wiring up dynamically using an IoC container (for example Castle Windsor) has over a tightly coupled system? I know that a detailed answer would depend on what the IoC was being used for, but I'm really just trying to get a feel for the magnitude of effort involved in the IoC work. Does anyone have any stats or other resources regarding this? Thanks

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  • Create swipe controlled simple flipbook style animation in ObjC

    - by eco_bach
    Hi I am a beginner in Obj C development, though quite experienced (over 10 years) with other ECMAscript based languages and OOP development. I want to build a simple flipbook style animation, controlled through swiping motion. I'm sure extremely simple for any advanced ObjC coders. Can anyone with extensive ObjC-CocoaTouch experience give me some higher level recommendations? ie, 1 -general application design, should I start with a simple view based application, or navigation based or? 2 -should I use 3rd party animation frameworks such as Cocos2D, or stick with built in classes and methods? 3 -if using built in methods, classes, what is the recommended way of achieving a animation, that will be controlled via swipe and touch gestures? 4 -I want to eventually have multiple 'flipbooks' that I can 'instantly' swap with one another, ie to give the net effect of an object changing color, etc, but not sure how to approach this from a memory management point of view, related to #1 above Except for point 3 above, I'm not expecting any actual code examples. Just general guidelines to follow and perhaps, what are some next steps I should take in my goal as an ObjC code samurai.

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  • PHP MVC: How to implement an effective Controller/View Association like ZendFramework guys do!

    - by Navi
    Hi, I am making my own PHP-MVC framework. i have a question regarding Controller and View Association. I love the way Zend framework uses view within Controller as follow: $this->view->data = 'Data here'; so it can be used in view as follow: echo $this->data; I am wondering how can i implement this association. I want to remove codes between /** **/ and want to replace with some magic functions. My codes for controller as as follow: class UserController extends Controller{ /************************************/ public function __construct(){ $this->view = new View(); $this->view->setLayout( 'home' ); } function __destruct(){ $this->view->render(); } /************************************/ public function index(){ $this->redirect('user/login'); } public function login(){ } public function register(){ } public function forgotPassword(){ } } Thanks and best regards, -Navi

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