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  • Are Multiple Iterators possible in php?

    - by artvolk
    Good day! I know that C# allows multiple iterators using yield, like described here: http://stackoverflow.com/questions/1754041/is-multiple-iterators-is-possible-in-c In PHP there is and Iterator interface. Is it possible to implement more than one iteration scenario for a class? More details (EDIT): For example I have class TreeNode implementing single tree node. The whole tree can be expressed using only one this class. I want to provide iterators for iterating all direct and indirect children of current node, for example using BreadthFirst or DepthFirst order. I can implement this Iterators as separate classes but doing so I need that tree node should expose it's children collection as public. C# pseudocode: public class TreeNode<T> { ... public IEnumerable<T> DepthFirstEnumerator { get { // Some tree traversal using 'yield return' } } public IEnumerable<T> BreadthFirstEnumerator { get { // Some tree traversal using 'yield return' } } }

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  • LINQ Datacontext Disposal Issues

    - by Refracted Paladin
    I am getting a Cannot access object: DataContext after it's been disposed in the below DAL method. I thought that I would be okay calling dispose there. result is an IEnumurable and I thought it was IQueryable that caused these kinds of problems. What am I doing wrong? How SHOULD I be disposing of my DataContext. Is there something better to be returning then a DataTable? This is a Desktop app that points at SQL 2005. Example method that causes this error -- public static DataTable GetEnrolledMembers(Guid workerID) { var DB = CmoDataContext.Create(); var AllEnrollees = from enrollment in DB.tblCMOEnrollments where enrollment.CMOSocialWorkerID == workerID || enrollment.CMONurseID == workerID join supportWorker in DB.tblSupportWorkers on enrollment.EconomicSupportWorkerID equals supportWorker.SupportWorkerID into workerGroup from worker in workerGroup.DefaultIfEmpty() select new { enrollment.ClientID, enrollment.CMONurseID, enrollment.CMOSocialWorkerID, enrollment.EnrollmentDate, enrollment.DisenrollmentDate, ESFirstName = worker.FirstName, ESLastName = worker.LastName, ESPhone = worker.Phone }; var result = from enrollee in AllEnrollees.AsEnumerable() where (enrollee.DisenrollmentDate == null || enrollee.DisenrollmentDate > DateTime.Now) //let memberName = BLLConnect.MemberName(enrollee.ClientID) let lastName = BLLConnect.MemberLastName(enrollee.ClientID) let firstName = BLLConnect.MemberFirstName(enrollee.ClientID) orderby enrollee.DisenrollmentDate ascending, lastName ascending select new { enrollee.ClientID, //MemberName = memberName, LastName = lastName, FirstName = firstName, NurseName = BLLAspnetdb.NurseName(enrollee.CMONurseID), SocialWorkerName = BLLAspnetdb.SocialWorkerName(enrollee.CMOSocialWorkerID), enrollee.EnrollmentDate, enrollee.DisenrollmentDate, ESWorkerName = enrollee.ESFirstName + " " + enrollee.ESLastName, enrollee.ESPhone }; DB.Dispose(); return result.CopyLinqToDataTable(); } partial class where I create the DataContext -- partial class CmoDataContext { public static bool IsDisconnectedUser { get { return Settings.Default.IsDisconnectedUser; } } public static CmoDataContext Create() { var cs = IsDisconnectedUser ? Settings.Default.CMOConnectionString : Settings.Default.Central_CMOConnectionString; return new CmoDataContext(cs); }

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  • What is a 'thunk'?

    - by fbrereto
    I've seen it used in programming (specifically in the C++ domain) and have no idea what it is. Presumably it is a design pattern, but I could be wrong. Can anyone give a good example of a thunk?

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  • Register all GUI components as Observers or pass current object to next object as a constructor argu

    - by Jack
    First, I'd like to say that I think this is a common issue and there may be a simple or common solution that I am unaware of. Many have probably encountered a similar problem. Thanks for reading. I am creating a GUI where each component needs to communicate (or at least be updated) by multiple other components. Currently, I'm using a Singleton class to accomplish this goal. Each GUI component gets the instance of the singleton and registers itself. When updates need to be made, the singleton can call public methods in the registered class. I think this is similar to an Observer pattern, but the singleton has more control. Currently, the program is set up something like this: class c1 { CommClass cc; c1() { cc = CommClass.getCommClass(); cc.registerC1( this ); C2 c2 = new c2(); } } class c2 { CommClass cc; c2() { cc = CommClass.getCommClass(); cc.registerC2( this ); C3 c3 = new c3(); } } class c3 { CommClass cc; c3() { cc = CommClass.getCommClass(); cc.registerC3( this ); C4 c4 = new c4(); } } etc. Unfortunately, the singleton class keeps growing larger as more communication is required between the components. I was wondering if it's a good idea to instead of using this singleton, pass the higher order GUI components as arguments in the constructors of each GUI component: class c1 { c1() { C2 c2 = new c2( this ); } } class c2 { C1 c1; c2( C1 c1 ) { this.c1 = c1 C3 c3 = new c3( c1, this ); } } class c3 { C1 c1; C2 c2; c3( C1 c1, C2 c2 ) { this.c1 = c1; this.c2 = c2; C4 c4 = new c4( c1, c2, this ); } } etc. The second version relies less on the CommClass, but it's still very messy as the private member variables increase in number and the constructors grow in length. Each class contains GUI components that need to communicate through CommClass, but I can't think of a good way to do it. If this seems strange or horribly inefficient, please describe some method of communication between classes that will continue to work as the project grows. Also, if this doesn't make any sense to anyone, I'll try to give actual code snippets in the future and think of a better way to ask the question. Thanks.

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  • What damage is done by document.write()?

    - by Simon Gibbs
    What bad things happen at the moment document.write() is invoked? I've heard bits and peices about document.write having an adverse impact on the DOM or on the use of Javascript libraries. I have an issue in front of me that I suspect is related, but have not been able to find a concise summary of what damage the method does.

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  • MVC architectural question - Where should payment processing go?

    - by Keltex
    This question is related to my ASP.NET MVC 2 development, but it could apply to any MVC environment and a question of where the logic should go. So let's say I have a controller that takes an online payment such as a shopping cart application. And I have the method that accepts the customers' credit card information: public class CartController : Controller CartRepository cartRepository = new CartRepository() [HttpPost] public ActionResult Payment(PaymentViewModel rec) { if(!ModelState.IsValid) { return View(rec); } // process payment here return RedirectToAction("Receipt"); } At the comment process payment here should the payment processing be handled: In the controller? By the repository? Someplace else?

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  • Using C Structs which contains ObjC Objects?

    - by GuidoMB
    I'm using C structs in objc and I've created a function that assembles the structure like the one from the Cocoa API. The things is that this structure is not like NSRect o NSPoint this structure packs objc objects soo I'm seeing a potential memory leak here. Do I need to provide a function to 'release' the structure? I'am not creating a ISKNewsCategory class because there will be no behavior but Do you think this is a good approach or I should define the class even doe there will be no behavior? typedef struct ISK_NewsCategory { NSString *name; NSString *code } ISKNewsCategory; NS_INLINE ISKNewsCategory ISKMakeNewsCategory(NSString *name, NSString *code) { ISKNewsCategory category; category.name = [name retain]; category.code = [code retain]; return category; }

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  • "Public" nested classes or not

    - by Frederick
    Suppose I have a class 'Application'. In order to be initialised it takes certain settings in the constructor. Let's also assume that the number of settings is so many that it's compelling to place them in a class of their own. Compare the following two implementations of this scenario. Implementation 1: class Application { Application(ApplicationSettings settings) { //Do initialisation here } } class ApplicationSettings { //Settings related methods and properties here } Implementation 2: class Application { Application(Application.Settings settings) { //Do initialisation here } class Settings { //Settings related methods and properties here } } To me, the second approach is very much preferable. It is more readable because it strongly emphasises the relation between the two classes. When I write code to instantiate Application class anywhere, the second approach is going to look prettier. Now just imagine the Settings class itself in turn had some similarly "related" class and that class in turn did so too. Go only three such levels and the class naming gets out out of hand in the 'non-nested' case. If you nest, however, things still stay elegant. Despite the above, I've read people saying on StackOverflow that nested classes are justified only if they're not visible to the outside world; that is if they are used only for the internal implementation of the containing class. The commonly cited objection is bloating the size of containing class's source file, but partial classes is the perfect solution for that problem. My question is, why are we wary of the "publicly exposed" use of nested classes? Are there any other arguments against such use?

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  • In Drupal 6, is there a way to take a custom field from the latest post to a taxonomy term, and disp

    - by user278457
    The title for this question pretty much sums up what I'm asking. I've got a list of taxonomy terms, and I'm using a view to display the latest post to each one. I'd like to also display a custom field set up in CCK just under this. Currently, I'm just using "date updated" of the taxonomy term itself which was easy to set up in views. I'd like to drill a little deeper and get the custom "event date" field I've added to the content type last posted to the taxonomy term I'm "viewing". I've got a feeling I'm going to have to write my own database query for this. If (I can avoid that){ How do I set up such a view? } Else{ What's the best practice for including lower level database queries alongside views? }

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  • Spring MVC Best Practice Handling Unrecoverable Exceptions In Controller

    - by jboyd
    When you have a controller that does logic with services and DAO's that may throw an unrecoverable exception, what is the best practice in dealing with those method calls? Currently an app I'm working on has very lengthy try catch methods that simply err.out exception messages, this doesn't seem very robust and I think that this code smells, is there any cookie cutter best practice for handling this in spring-mvc?

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  • What is the best way to post data from web browser to server?

    - by Kronass
    Hi, I want to know what is the best way to send data from web browser to server using post method. I've seen a practice where they wrap all the elements data in XML, convert it into Base64 string and then post it to the server (via Ajax or hidden field). this way will not work if the Javascript is disabled, any how if I ignored this. is it a good practice to wrap elements into XML (or create my custom wrapper in general) and post them to server saying it will enhance the maintainability of the code or just stick with the classical way and no need to add unnecessary text in the post.

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  • When should I be cautious using about data binding in .NET?

    - by Ben McCormack
    I just started working on a small team of .NET programmers about a month ago and recently got in a discussion with our team lead regarding why we don't use databinding at all in our code. Every time we work with a data grid, we iterate through a data table and populate the grid row by row; the code usually looks something like this: Dim dt as DataTable = FuncLib.GetData("spGetTheData ...") Dim i As Integer For i = 0 To dt.Rows.Length - 1 '(not sure why we do not use a for each here)' gridRow = grid.Rows.Add() gridRow(constantProductID).Value = dt("ProductID").Value gridRow(constantProductDesc).Value = dt("ProductDescription").Value Next '(I am probably missing something in the code, but that is basically it)' Our team lead was saying that he got burned using data binding when working with Sheridan Grid controls, VB6, and ADO recordsets back in the nineties. He's not sure what the exact problem was, but he remembers that binding didn't work as expected and caused him some major problems. Since then, they haven't trusted data binding and load the data for all their controls by hand. The reason the conversation even came up was because I found data binding to be very simple and really liked separating the data presentation (in this case, the data grid) from the in-memory data source (in this case, the data table). "Loading" the data row by row into the grid seemed to break this distinction. I also observed that with the advent of XAML in WPF and Silverlight, data-binding seems like a must-have in order to be able to cleanly wire up a designer's XAML code with your data. When should I be cautious of using data-binding in .NET?

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  • Which design pattern to manage windows?

    - by Lu Lu
    Hello, I am using .NET 2.0 & C# to develop a WinForm Mdi application. It will have a Main Window and a lot of mdi windows. I am thinking I should use which design pattern to manage mdi windows. Because I want only one instance for each window, if window is existed, I will show it on top, & otherwise I will create and show it. Note: a mdi window is opened from Menus of Main Window or open from another mdi window. An example is very good. Update: Menu's status is depended on mdi window's status. Ex: If Window 'A' is openned - menu 'A' - disabled. When window 'A' is closed - I update menu 'A' status to Enabled. Thanks.

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  • How to automatically fix MISSING reference in a dll when a referenced library is broken in VB6?

    - by systempuntoout
    What do you do when you break compatibility on a common library used by many other libraries? What i usually do is: For every dll that reference the broken one Checkout dll Checkout vbp project Open vpb project with VB6 Ide Click on References button Uncheck MISSING reference and OK Click on References button Check references and OK Click on Make dll Close project This can be a pita activity, when you have many Dll to recompile and it can be error prone because you could miss some Dll (anyway we have continuous integration that alert this cases). What's your best practice to handle this scenario?

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  • Should I map a domain object to a view model using an optional constructor?

    - by Byron Sommardahl
    I'd like to be able to map a domain model to a view model by newing up a view model and passing in the contributing domain model as a parameter (like the code below). My motivation is to keep from re-using mapping code AND to provide a simple way to map (not using automapper yet). A friend says the view model should not know anything about the "payment" domain model that's being passed into the optional constructor. What do you think? public class LineItemsViewModel { public LineItemsViewModel() { } public LineItemsViewModel(IPayment payment) { LineItemColumnHeaders = payment.MerchantContext.Profile.UiPreferences.LineItemColumnHeaders; LineItems = LineItemDomainToViewModelMapper.MapToViewModel(payment.LineItems); ConvenienceFeeAmount = payment.ConvenienceFee.Fee; SubTotal = payment.PaymentAmount; Total = payment.PaymentAmount + payment.ConvenienceFee.Fee; } public IEnumerable<Dictionary<int, string>> LineItems { get; set; } public Dictionary<int, string> LineItemColumnHeaders { get; set; } public decimal SubTotal { get; set; } public decimal ConvenienceFeeAmount { get; set; } public decimal Total { get; set; } }

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  • Question regarding factory pattern

    - by eriks
    I have a factory class to build objects of base class B. The object (D) that uses this factory received a list of strings representing the actual types. What is the correct implementation: the factory receives an Enum (and uses switch inside the Create function) and D is responsible to convert the string to Enum. the factory receives a string and checks for a match to a set of valid strings (using ifs') other implementation i didn't think of.

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  • ASP.Net MVC Where do you convert from Entities to ViewModels?

    - by Pino
    Title pretty much explains it all, its the last thing I'm trying to work into our project. We are structured with a Service Library which contains a function like so. /// <summary> /// Returns a single category based on the specified ID. /// </summary> public Category GetCategory(int CategoryID) { var RetVal = _session.Single<Category>(x => x.ID == CategoryID); return RetVal; } Now Category is a Entity (We are using Entity Framework) we need to convert that to a CategoryViewModel. Now, how would people structure this? Would you make sure the service function returned a CategoryViewModel? Have the controller pull the data from the service then call another function to covnert to a view model?

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  • Finite State Machine : Bad design?

    - by f4
    Are Finite State Machines generally considered as bad design in OOP ? I hear that a lot. And, after I had to work on a really old, undocumented piece of C++ making use of it, I tend to agree. It was a pain to debug. what about readability/maintainability concerns?

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  • How to refactor use of the general Exception?

    - by Colin
    Our code catches the general exception everywhere. Usually it writes the error to a log table in the database and shows a MessageBox to the user to say that the operation requested failed. If there is database interaction, the transaction is rolled back. I have introduced a business logic layer and a data access layer to unravel some of the logic. In the data access layer, I have chosen not to catch anything and I also throw ArgumentNullExceptions and ArgumentOutOfRangeExceptions so that the message passed up the stack does not come straight from the database. In the business logic layer I put a try catch. In the catch I rollback the transaction, do the logging and rethrow. In the presentation layer there is another try catch that displays a MessageBox. I am now thinking about catching a DataException and an ArgumentException instead of an Exception where I know the code only accesses a database. Where the code accesses a web service, then I thought I would create my own "WebServiceException", which would be created in the data access layer whenever an HttpException, WebException or SoapException is thrown. So now, generally I will be catching 2 or 3 exceptions where currently I catch just the general Exception, and I think that seems OK to me. Does anyone wrap exceptions up again to carry the message up to the presentation layer? I think I should probably add a try catch to Main() that catches Exception, attempts to log it, displays an "Application has encountered an error" message and exits the application. So, my question is, does anyone see any holes in my plan? Are there any obvious exceptions that I should be catching or do these ones pretty much cover it (other than file access - I think there is only 1 place where we read-write to a config file).

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  • How to determine which inheriting class is using an abstract class' methods.

    - by Kin
    In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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

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

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  • Circular Dependency Solution

    - by gfoley
    Our current project has ran into a circular dependency issue. Our business logic assembly is using classes and static methods from our SharedLibrary assembly. The SharedLibrary contains a whole bunch of helper functions, such as a SQL Reader class, Enumerators, Global Variables, Error Handling, Logging and Validation. The SharedLibrary needs access to the Business objects, but the Business objects need access to SharedLibrary. The old developers solved this obvious code smell by replicating the functionality of the business objects in the shared library (very anti-DRY). I've spent a day now trying to read about my options to solve this but i'm hitting a dead end. I'm open to the idea of architecture redesign, but only as a last resort. So how can i have a Shared Helper Library which can access the business objects, with the business objects still accessing the Shared Helper Library?

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