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  • How to design this class hierarchy?

    - by devoured elysium
    I have defined an Event class: Event and all the following classes inherit from Event: AEvent BEvent CEvent DEvent Now, with the info I gather from all these Event classes, I will make a chart. With AEvent and BEvent, I will generate points for that chart, while with CEvent and DEvent I will paint certain regions of the chart. Now, how should I signal this in my class hierarchy? Should I make AEvent and BEvent inherit from PointEvent while CEvent and DEvent inherit from RegionEvent, being that both RegionEvent and PointEvent inherit from Event? Should I add a field with an Enum to Event with 2 values, Point and Region, and each of the child classes set their value to it? Should I use some kind of pattern here? Which one? Thanks.

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  • What is the best testing pattern for checking that parameters are being used properly?

    - by Joseph
    I'm using Rhino Mocks to try to verify that when I call a certain method, that the method in turn will properly group items and then call another method. Something like this: //Arrange var bucketsOfFun = new BucketGame(); var balls = new List<IBall> { new Ball { Color = Color.Red }, new Ball { Color = Color.Blue }, new Ball { Color = Color.Yellow }, new Ball { Color = Color.Orange }, new Ball { Color = Color.Orange } }; //Act bucketsOfFun.HaveFunWithBucketsAndBalls(balls); //Assert ??? Here is where the trouble begins for me. My method is doing something like this: public void HaveFunWithBucketsAndBalls(IList<IBall> balls) { //group all the balls together according to color var blueBalls = GetBlueBalls(balls); var redBalls = GetRedBalls(balls); // you get the idea HaveFunWithABucketOfBalls(blueBalls); HaveFunWithABucketOfBalls(redBalls); // etc etc with all the different colors } public void HaveFunWithABucketOfBalls(IList<IBall> colorSpecificBalls) { //doing some stuff here that i don't care about //for the test i'm writing right now } What I want to assert is that each time I call HaveFunWithABucketOfBalls that I'm calling it with a group of 1 red ball, then 1 blue ball, then 1 yellow ball, then 2 orange balls. If I can assert that behavior then I can verify that the method is doing what I want it to do, which is grouping the balls properly. Any ideas of what the best testing pattern for this would be?

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  • Overly accessible and incredibly resource hungry relationships between business objects. How can I f

    - by Mike
    Hi, Firstly, This might seem like a long question. I don't think it is... The code is just an overview of what im currently doing. It doesn't feel right, so I am looking for constructive criticism and warnings for pitfalls and suggestions of what I can do. I have a database with business objects. I need to access properties of parent objects. I need to maintain some sort of state through business objects. If you look at the classes, I don't think that the access modifiers are right. I don't think its structured very well. Most of the relationships are modelled with public properties. SubAccount.Account.User.ID <-- all of those are public.. Is there a better way to model a relationship between classes than this so its not so "public"? The other part of this question is about resources: If I was to make a User.GetUserList() function that returns a List, and I had 9000 users, when I call the GetUsers method, it will make 9000 User objects and inside that it will make 9000 new AccountCollection objects. What can I do to make this project not so resource hungry? Please find the code below and rip it to shreds. public class User { public string ID {get;set;} public string FirstName {get; set;} public string LastName {get; set;} public string PhoneNo {get; set;} public AccountCollection accounts {get; set;} public User { accounts = new AccountCollection(this); } public static List<Users> GetUsers() { return Data.GetUsers(); } } public AccountCollection : IEnumerable<Account> { private User user; public AccountCollection(User user) { this.user = user; } public IEnumerable<Account> GetEnumerator() { return Data.GetAccounts(user); } } public class Account { public User User {get; set;} //This is public so that the subaccount can access its Account's User's ID public int ID; public string Name; public Account(User user) { this.user = user; } } public SubAccountCollection : IEnumerable<SubAccount> { public Account account {get; set;} public SubAccountCollection(Account account) { this.account = account; } public IEnumerable<SubAccount> GetEnumerator() { return Data.GetSubAccounts(account); } } public class SubAccount { public Account account {get; set;} //this is public so that my Data class can access the account, to get the account's user's ID. public SubAccount(Account account) { this.account = account; } public Report GenerateReport() { Data.GetReport(this); } } public static class Data { public static List<Account> GetSubAccounts(Account account) { using (var dc = new databaseDataContext()) { List<SubAccount> query = (from a in dc.Accounts where a.UserID == account.User.ID //this is getting the account's user's ID select new SubAccount(account) { ID = a.ID, Name = a.Name, }).ToList(); } } public static List<Account> GetAccounts(User user) { using (var dc = new databaseDataContext()) { List<Account> query = (from a in dc.Accounts where a.UserID == User.ID //this is getting the user's ID select new Account(user) { ID = a.ID, Name = a.Name, }).ToList(); } } public static Report GetReport(SubAccount subAccount) { Report report = new Report(); //database access code here //need to get the user id of the subaccount's account for data querying. //i've got the subaccount, but how should i get the user id. //i would imagine something like this: int accountID = subAccount.Account.User.ID; //but this would require the subaccount's Account property to be public. //i do not want this to be accessible from my other project (UI). //reading up on internal seems to do the trick, but within my code it still feels //public. I could restrict the property to read, and only private set. return report; } public static List<User> GetUsers() { using (var dc = new databaseDataContext()) { var query = (from u in dc.Users select new User { ID = u.ID, FirstName = u.FirstName, LastName = u.LastName, PhoneNo = u.PhoneNo }).ToList(); return query; } } }

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  • Is ASP.NET MVC is really MVC? Or how to separate model from controller?

    - by Andrey
    Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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  • Ideal way to cancel an executing AsyncTask

    - by Samuh
    I am running remote audio-file-fetching and audio file playback operations in a background thread using AsyncTask. A Cancellable progress bar is shown for the time the fetch operation runs. I want to cancel/abort the AsyncTask run when the user cancels (decides against) the operation. What is the ideal way to handle such a case?

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  • Interface Design Problem: Storing Result of Transactions

    - by jboyd
    Requirements: multiple sources of input (social media content) into a system multiple destinations of output (social media api's) sources and destinations WILL be added some pseudo: IContentProvider contentProvider = context.getBean("contentProvider"); List<Content> toPost = contentProvider.getContent(); for (Content c : toPost) { SocialMediaPresence smPresence = socialMediaService.getSMPresenceBySomeId(c.getDestId()); smPresence.hasTwitter(); smPresence.hasFacebook(); //just to show what this is smPresence.postContent(c); //post content could fail for some SM platforms, but shoulnd't be lost forever } So now I run out of steam, I need to know what content has been successfully posted, and if it hasn't gone too all platforms, or if another platform were added in the future that content needs to go out for it as well (therefore my content provider will need to not only know if content has gone out, but for what platforms). I'm not looking for code, although sample/pseudo is fine... I'm looking for an approach to this problem that I can implement

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  • JDBC/OSGi and how to dynamically load drivers without explicitly stating dependencies in the bundle?

    - by Chris
    Hi, This is a biggie. I have a well-structured yet monolithic code base that has a primitive modular architecture (all modules implement interfaces yet share the same classpath). I realize the folly of this approach and the problems it represents when I go to deploy on application servers that may have different conflicting versions of my library. I'm dependent on around 30 jars right now and am mid-way though bnding them up. Now some of my modules are easy to declare the versioned dependencies of, such as my networking components. They statically reference classes within the JRE and other BNDded libraries but my JDBC related components instantiate via Class.forName(...) and can use one of any number of drivers. I am breaking everything up into OSGi bundles by service area. My core classes/interfaces. Reporting related components. Database access related components (via JDBC). etc.... I wish for my code to be able to still be used without OSGi via single jar file with all my dependencies and without OSGi at all (via JARJAR) and also to be modular via the OSGi meta-data and granular bundles with dependency information. How do I configure my bundle and my code so that it can dynamically utilize any driver on the classpath and/or within the OSGi container environment (Felix/Equinox/etc.)? Is there a run-time method to detect if I am running in an OSGi container that is compatible across containers (Felix/Equinox/etc.) ? Do I need to use a different class loading mechanism if I am in a OSGi container? Am I required to import OSGi classes into my project to be able to load an at-bundle-time-unknown JDBC driver via my database module? I also have a second method of obtaining a driver (via JNDI, which is only really applicable when running in an app server), do I need to change my JNDI access code for OSGi-aware app servers?

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  • How to avoid using this in a constructor

    - by Paralife
    I have this situation: interface MessageListener { void onMessageReceipt(Message message); } class MessageReceiver { MessageListener listener; public MessageReceiver(MessageListener listener, other arguments...) { this.listener = listener; } loop() { Message message = nextMessage(); listener.onMessageReceipt(message); } } and I want to avoid the following pattern: (Using the this in the Client constructor) class Client implements MessageListener { MessageReceiver receiver; MessageSender sender; public Client(...) { receiver = new MessageReceiver(this, other arguments...); sender = new Sender(...); } . . . @Override public void onMessageReceipt(Message message) { if(Message.isGood()) sender.send("Congrtulations"); else sender.send("Boooooooo"); } } The reason why i need the above functionality is because i want to call the sender inside the onMessageReceipt() function, for example to send a reply. But I dont want to pass the sender into a listener, so the only way I can think of is containing the sender in a class that implements the listener, hence the above resulting Client implementation. Is there a way to achive this without the use of 'this' in the constructor? It feels bizare and i dont like it, since i am passing myself to an object(MessageReceiver) before I am fully constructed. On the other hand, the MessageReceiver is not passed from outside, it is constructed inside, but does this 'purifies' the bizarre pattern? I am seeking for an alternative or an assurance of some kind that this is safe, or situations on which it might backfire on me.

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  • Separation of concerns and authentication

    - by Tom Gilder
    I'm trying to be a Good Developer and separate my concerns out. I've got an ASP.NET MVC project with all my web code, and a DAL project with all the model code. Sometimes code in the DAL needs to check if the current user is authorized to perform some actions, by checking something like CurrentUser.IsAdmin. For the web site, the current is derived from the Windows username (from HttpContext.Current.User.Identity), but this is clearly a web concern and shouldn't be coupled to the DAL. What's the best pattern to loosely couple the authentication? Should the DAL be asking the MVC code for a username, or the MVC be telling the DAL? Are there advantages or disadvantages to one or the other? Thank you!

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  • How to change easily between ajax-based website and basic HTML website?

    - by A.S al-shammari
    Hi, I have a website ( based on JSP/Servlets ,using MVC pattern), and I want to support AJAX-based website and basic HTML-based website. website visitors should be able to change the surfing mode from Ajax to basic HTML and vise versa, - as it applies in Google-mail. The Questions : What is the best way to achieve this goal easily? Should I design two views for each page? I use JQuery and JSON as the result of this answer.

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  • Is there a Standard or Best Practice for Perl Progams, as opposed to Perl Modules?

    - by swestrup
    I've written any number of perl modules in the past, and more than a few stand-alone perl programs, but I've never released a multi-file perl program into the wild before. I have a perl program that is almost at the beta stage and is going to be released open source. It requires a number of data files, as well as some external perl modules -- some I've written myself, and some from CPAN -- that I'll have to bundle with it so as to ensure that someone can just download my program and install it without worrying about hunting for obscure modules. So, it sounds to me like I need to write an installer to copy all the files to standard locations so that a user can easily install everything. The trouble is, I have no idea what the standard practice would be for this. I have found lots of tutorials on perl module standards, but none on perl program standards. Does anyone have any pointers to standard paths, installation proceedures, etc, for perl programs? This is going to be complicated by the fact that the program is multi-platform. I've been testing it in Linux, but its designed to work equally well in Windows.

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  • Why is it preferable to call a static method statically from within an instance of the method's clas

    - by javanix
    If I create an instance of a class in Java, why is it preferable to call a static method of that same class statically, rather than using this.method()? I get a warning from Eclipse when I try to call static method staticMethod() from within the custom class's constructor via this.staticMethod(). public MyClass() { this.staticMethod(); } vs public MyClass() { MyClass.staticMethod(); } Can anyone explain why this is a bad thing to do? It seems to me like the compiler should already have allocated an instance of the object, so statically allocating memory would be unneeded overhead.

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  • Downloading RSS using python

    - by Vojtech R.
    Hi, I have list of 200 rss feeds, which I have to downloading. It's continuous process - I have to download every post, nothing can be missing, but also no duplicates. So best practice should be remember last update of feed and control it for change in x-hour interval? And how to handle if downloader will be restarted? So downloader should remember, what were downloaded and dont download it again... It's somewhere implemented yet? Or any tips for article? Thanks

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  • Which Code Should Go Where in MVC Structure

    - by Oguz
    My problem is in somewhere between model and controller.Everything works perfect for me when I use MVC just for crud (create, read, update, delete).I have separate models for each database table .I access these models from controller , to crud them . For example , in contacts application,I have actions (create, read, update, delete) in controller(contact) to use model's (contact) methods (create, read, update, delete). The problem starts when I try to do something more complicated. There are some complex processes which I do not know where should I put them. For example , in registering user process. I can not just finish this process in user model because , I have to use other models too (sending mails , creating other records for user via other models) and do lots of complex validations via other models. For example , in some complex searching processes , I have to access lots of models (articles, videos, images etc.) Or, sometimes , I have to use apis to decide what I will do next or which database model I will use to record data So where is the place to do this complicated processes. I do not want to do them in controllers , Because sometimes I should use these processes in other controllers too. And I do not want to put these process in models because , I use models as database access layers .May be I am wrong,I want to know . Thank you for your answer .

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  • Abstract Factory Using Generics: Is Explicitly Converting a Specified Type to Generic a Bad Practice

    - by Merritt
    The question's title says it all. I like how it fits into the rest of my code, but does it smell? public interface IFoo<T> { T Bar { get; set; } } public class StringFoo : IFoo<string> { public string Bar { get; set; } } public static class FooFactory { public static IFoo<T> CreateFoo<T>() { if (typeof(T) == typeof(string)) { return new StringFoo() as IFoo<T>; } throw new NotImplementedException(); } } UPDATE: this is sort of a duplicate of Is the StaticFactory in codecampserver a well known pattern?

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  • Can you find a pattern to sync files knowing only dates and filenames?

    - by Robert MacLean
    Imagine if you will a operating system that had the following methods for files Create File: Creates (writes) a new file to disk. Calling this if a file exists causes a fault. Update File: Updates an existing file. Call this if a file doesn't exist causes a fault. Read File: Reads data from a file. Enumerate files: Gets all files in a folder. Files themselves in this operating system only have the following meta data: Created Time: The original date and time the file was created, by the Create File method. Modified Time: The date and time the file was last modified by the Update File method. If the file has never been modified, this will equal the Create Time. You have been given the task of writing an application which will sync the files between two directories (lets call them bill and ted) on a machine. However it is not that simple, the client has required that The application never faults (see methods above). That while the application is running the users can add and update files and those will be sync'd next time the application runs. Files can be added to either the ted or bill directories. File names cannot be altered. The application will perform one sync per time it is run. The application must be almost entirely in memory, in other words you cannot create a log of filenames and write that to disk and then check that the next time. The exception to point 6 is that you can store date and times between runs. Each date/time is associated with a key labeled A through J (so you have 10 to use) so you can compare keys between runs. There is no way to catch exceptions in the application. Answer will be accepted based on the following conditions: First answer to meet all requirements will be accepted. If there is no way to meet all requirements, the answer which ensures the smallest amount of missed changes per sync will be accepted. A bounty will be created (100 points) as soon as possible for the prize. The winner will be selected one day before the bounty ends. Please ask questions in the comments and I will gladly update and refine the question on those.

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  • What should a developer know before building a public web site?

    - by Joel Coehoorn
    What things should a programmer implementing the technical details of a web site address before making the site public? If Jeff Atwood can forget about HttpOnly cookies, sitemaps, and cross-site request forgeries all in the same site, what important thing could I be forgetting as well? I'm thinking about this from a web developer's perspective, such that someone else is creating the actual design and content for the site. So while usability and content may be more important than the platform, you the programmer have little say in that. What you do need to worry about is that your implementation of the platform is stable, performs well, is secure, and meets any other business goals (like not cost too much, take too long to build, and rank as well with Google as the content supports). Think of this from the perspective of a developer who's done some work for intranet-type applications in a fairly trusted environment, and is about to have his first shot and putting out a potentially popular site for the entire big bad world wide web. Also: I'm looking for something more specific than just a vague "web standards" response. I mean, HTML, JavaScript, and CSS over HTTP are pretty much a given, especially when I've already specified that you're a professional web developer. So going beyond that, Which standards? In what circumstances, and why? Provide a link to the standard's specification. This question is community wiki, so please feel free to edit that answer to add links to good articles that will help explain or teach each particular point.

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  • When to use "property" builtin: auxiliary functions and generators

    - by Seth Johnson
    I recently discovered Python's property built-in, which disguises class method getters and setters as a class's property. I'm now being tempted to use it in ways that I'm pretty sure are inappropriate. Using the property keyword is clearly the right thing to do if class A has a property _x whose allowable values you want to restrict; i.e., it would replace the getX() and setX() construction one might write in C++. But where else is it appropriate to make a function a property? For example, if you have class Vertex(object): def __init__(self): self.x = 0.0 self.y = 1.0 class Polygon(object): def __init__(self, list_of_vertices): self.vertices = list_of_vertices def get_vertex_positions(self): return zip( *( (v.x,v.y) for v in self.vertices ) ) is it appropriate to add vertex_positions = property( get_vertex_positions ) ? Is it ever ok to make a generator look like a property? Imagine if a change in our code meant that we no longer stored Polygon.vertices the same way. Would it then be ok to add this to Polygon? @property def vertices(self): for v in self._new_v_thing: yield v.calculate_equivalent_vertex()

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  • Strategy for unsubscribing event handlers

    - by stiank81
    In my WPF application I have a View that is given a ViewModel, and when given this View it adds event handlers to the ViewModel's PropertyChanged event. When some action occur in the GUI I remove the View and add another View to the holding container - where this new one is bound to the same ViewModel. After this has happened the old View still keeps handling PropertyChanged events in the ViewModel. I'm assuming this happens because the View hasn't been collected by the Garbage Collector yet, and therefore is alive? Well - I need it to stop. My assumption is that I need to manually detach the event handler from the ViewModel? Is there a best-practice on how to handle this?

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  • SVN best practice - checking out root folder

    - by Stephen Dolier
    Hi all, quick question about svn checkout best practice. Once the structure of a repository is set up, ie trunk, branches, tags, is it normal to have the root checked out to our local machines. Or should you only check out the trunk if that's what you are working on or a branch if we so choose to create one. The reason i ask is that every time someone creates a branch or tag we all get a copy when we do an update. btw, we're recently migrated from vss.

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