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  • Java generics question

    - by user247866
    So I have 3 classes. Abstract class A Class B extends class A independent Class C In class D that contains the main method, I create a list of instances of class B List<B> b = methodCall(); // the method returns a list of instances of class B Now in class C I have one method that is common to both A and B, and hence I don't want to duplicate it. I want to have one method that takes as input an instance of class A, as follows: public void someMethod(List<A> a) However, when I do: C c = new C(); c.someMethod(b); I get an error that some-method is not applicable for the argument List<B>, instead it's expecting to get List<A>. Is there a good way to fix this problem? Many thanks!

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  • Making OR/M loosely coupled and abstracted away from other layers.

    - by Genuine
    Hi all. In an n-tier architecture, the best place to put an object-relational mapping (OR/M) code is in the data access layer. For example, database queries and updates can be delegated to a tool like NHibernate. Yet, I'd like to keep all references to NHibernate within the data access layer and abstract dependencies away from the layers below or above it. That way, I can swap or plug in another OR/M tool (e.g. Entity Framework) or some approach (e.g. plain vanilla stored procedure calls, mock objects) without causing compile-time errors or a major overhaul of the entire application. Testability is an added bonus. Could someone please suggest a wrapper (i.e. an interface or base class) or approach that would keep OR/M loosely coupled and contained in 1 layer? Or point me to resources that would help? Thanks.

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  • Custom OData operation / customize EF model to hide join table in many-to-many relationship

    - by AC
    I've got a data model that has two tables with a join table for a many to many relationship & creating an OData service to expose the data for CRUD ops in a Silverlight app. What I'd like to do is abstract the join table from the service. I'm not sure if the best way to do this would be in the model (using EF in .NET3.5SP1) or if I should do it with a custom service operation. If I do it in the EF model (not sure how I'd do this), then the OOTB WCF Data Service stuff would make it easy to say [..]/Courses(1)/Modules ... otherwise I'd have to create a custom operation to do this. Is it possible to do this in the EF model and if so, how does that work?

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  • C#: reflection alternative for switch on enum in order to select namespace/class

    - by Am
    Hi, I have an interface named IHarvester. There are 3 implementations of that interface, each under their own namespace: Google Yahoo Bing A HarvesterManager uses the given harvester. It knows the interface and all 3 implementations. I want some way of letting the class user say in which harvester it wants to use. And in the code select that implementation, without a switch-case implementation. Can reflection save my day? Here is the code bits: // repeat for each harvester namespace Harvester.Google { public abstract class Fetcher : BaseHarvester, IInfoHarvester {...} } public enum HarvestingSource { Google, Yahoo, Bing, } class HarvesterManager { public HarvestingSource PreferedSource {get;set;} public HarvestSomthing() { switch (PreferedSource) .... // awful... } } Thanks.

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • C#: why Base class is allowed to implement an interface contract without inheriting from it?

    - by etarassov
    I've stumbled upon this "feature" of C# - the base class that implements interface methods does not have to derive from it. Example: public interface IContract { void Func(); } // Note that Base does **not** derive from IContract public abstract class Base { public void Func() { Console.WriteLine("Base.Func"); } } // Note that Derived does *not* provide implementation for IContract public class Derived : Base, IContract { } What happens is that Derived magically picks-up a public method Base.Func and decides that it will implement IContract.Func. What is the reason behind this magic? IMHO: this "quasi-implementation" feature is very-unintuitive and make code-inspection much harder. What do you think?

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  • MVC & Design patterns in C++

    - by theunanonim
    I have an assignment (university level) in C++ The application that was done so far: - MVC agenda - the views are command-line - Agenda contains a list of contacts - a contact may be a friend or an acquiantance - Agenda may contain also a Company that is a contact and may contain other contacts (sorry the code is already too big as I tried to keep the MVC aspect of the application, and I can't post it here or request your time to study it..) To do: - implement factory method pattern - implement observer pattern - implement strategy pattern - implement visitor pattern The evaluation will depend on the number of added patterns and places they have been added. Am I an idiot or this is the stupidies possible assignement ? If not, please help me with some basic tips.. which one where ? Best Regards. P.S. Sorry for my English

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  • Passing dependent objects to a parent constructor in Scala

    - by Nick Johnson
    Suppose I have the following class heirarchy: class A() class B(a:A) class C(b:B) class BaseClass(b:B, c:C) Now I want to implement a subclass of BaseClass, which is given an instance of A, and constructs instances of B and C, which it passes to its superclass constructor. If I could use arbitrary expressions, I'd do something like this: b = new B(a) c = new C(b) super(b, c) Because the second argument to the parent constructor depends on the value of the first argument, though, I can't see any way to do this, without using a factory function, or a gratuitous hack, such as : class IntermediateSubclass(b:B) extends BaseClass(b, new C(b)) class RealSubclass(a:A) extends IntermediateSubclass(new B(a)) Is there clean way to do this?

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  • Are today's young programmers getting wrapped around the axle with patterns and practices?

    - by Robert Harvey
    Recently I have noticed a number of questions on SO that look something like this: I am writing a small program to keep a list of the songs that I keep on my ipod. I'm thinking about writing it as a 3-tier MVC Ruby on Rails web application with TDD, DDD and IOC, using a factory pattern to create the classes and a singleton to store my application settings. Do you think I'm taking the right approach? Do you think that we're handing novice programmers a very sharp knife and telling them, "Don't cut yourself with this"? NOTE: Despite the humorous tone, this is a serious (and programming-related) question.

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  • What is the initiating actor for the usecase shown here

    - by Illep
    I am new to drawing use case and writing use case descriptions. I have an Actor called User , an abstract usecase called Work Type and another use case called Manager. The usecase Manager has a generalized relationship with the Work Type use case. I'm now writing the use case description for Manager use case. And what is the initiating Actor for this use case. Is it the Actor User ? or doesn't it have an initiating Actor ? Note: I only want to know the initiating Actor for the use case Manager

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  • Getting error in integrating Contacts APIs in Android 1.6 and 2.0

    - by dhaiwat
    Hi All, I have seen the BusinessCard example provide in Android examples. I am using ContactAccessor abstract class to seperate out the SDK versions. My code is running fine for 2.0 onwards, but when I am trying to build the code in Adnroid 1.6 I am getting the following errors: Build.VERSION_CODES.ECLAIR is not resolved. Getting errors in the whole class in which I have used Contacts APIs from 2.0 (say in class ContactAccessorSdk5.java). How to resolve these issues? I want to run my App on both the versions. Please help me. Regards, Dhaiwat Bhavsar.

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  • C# to Java Conversion: What is a [DefaultProperty("value")]?

    - by Shiftbit
    I do not understand how the DefaultProperty Metadata tag work or what it signifies. I've read the MSDN and went through the sample but I find it confusing. DefaultPropertyAttribute Class I've read a few blogs and they seem to refer to the indexers. I'm not sure why you would want metadata for your properties? I am coming from a Java background, perhaps a Java analogy would help. [DefaultProperty("Value")] public abstract class FOO<T> : ANY, IBAR<T> { public FOO() { } public FOO(T value) { this.Value = value; } public virtual T Value { get; set; } }

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  • .NET Forms Abstraction for WPF, Silverlight, Winforms, WebForms, etc...

    - by tyndall
    Anyone know of a project(s) that seek to abstract form definitions on level higher than WPF, Silverlight, Winforms, WebForms, etc... I'm working on a project where we are fixing up 16 somewhat simple WebForms. But we may convert (and probably will convert to WPF or Silverlight 3 to 4 months from now. I'd rather define these forms once and be done with it. I'm willing to write a small DSL to help define forms, subforms, validation, links, and popups. I'm only looking to solve this for 80% or 90% of the forms. Four are very complicated and I'm willing to hand code these. I guess I'm looking for something like what XUL had hoped to be.

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  • How to set order of appearance for fields when using Html.EditorFor in MVC 2?

    - by Anrie
    I have the following classes in my Model: public abstract class Entity : IEntity { [ScaffoldColumn(false)] public int Id { get; set; } [Required,StringLength(500)] public string Name { get; set; } } and public class Model : SortableEntity { [Required] public ModelType Type { get; set; } [ListRequired] public List<Producer> Producers { get; set; } public List<PrintArea> PrintAreas { get; set; } public List<Color> Colors { get; set; } } To display the "Model" class in the view I simply call Html.EditorFor(model=model), but the "Name" property of the base class is rendered last, which is not the desired behaviour. Is it possible to influenece on the order of displayed fields somehow?

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  • Fluent NHibernate + multiple databases

    - by Pablote
    My project needs to handle three databases, that means three session factories. The thing is if i do something like this with fluent nhibernate: .Mappings(m = m.FluentMappings.AddFromAssembly(Assembly.GetExecutingAssembly())) the factories would pick up all the mappings, even the ones that correspond to another database I've seen that when using automapping you can do something like this, and filter by namespace: .Mappings(m = m.AutoMappings.Add(AutoMap.AssemblyOf().Where(t = t.Namespace == "Storefront.Entities"))) I havent found anything like this for fluent mappings, is it possible?? The only solutions I can think of are: either create separate assemblies for each db mapping classes or explicitly adding each of the entities to the factory configuration. I would prefer to avoid both, if possible. Thanks.

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  • no ocijdbc10 in java.library.path

    - by B.Z.B
    Hey all, So I've been plagued by this issue, whenever I try to run my app in eclipse, I get this error. 2011-02-23 09:55:08,388 ERROR (com.xxxxx.services.factory.ServiceInvokerLocal:21) - java.lang.UnsatisfiedLinkError: no ocijdbc10 in java.library.path I've tried following the steps I found here with no luck. I've tried this on a XP VM as well as windows 7 (although in win 7 I get a different error, below) java.lang.UnsatisfiedLinkError: no ocijdbc9 in java.library.path I've made sure my oracle client was ok (by running TOAD) and I also re-added the classes12.jar / ojdbc14.jars to my WEB-INF/lib folder taken directly from my %ORACLE_HOME% folder (also re-added them to the lib path). I've also tried just adding the ojdbc14.jar without the classes12.jar. Any suggestions appreciated. In the XP VM I have my PATH variable set to C:\Program Files\Java\jdk1.6.0_24\bin;C:\ORACLE\product\10.2.0.1\BIN. I'm using Tomcat server 5.0

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  • Magento: Why do controller action predispatch events not fire if the controller is rewritten?

    - by mattalexx
    Why do controller action predispatch events not fire if the controller is rewritten? Here is a snippet of store/app/code/core/Mage/Core/Controller/Varien/Action.php: abstract class Mage_Core_Controller_Varien_Action { // [...] public function preDispatch() { // [...] if ($this->_rewrite()) { return; // [What is the purpose if this?] } // [...] // [This is where my event needs to be firing, but this code never gets // executed because the controller is rewritten] Mage::dispatchEvent( 'controller_action_predispatch_'.$this->getFullActionName(), array('controller_action'=>$this) ); } // [...] } I don't know where to start fixing this problem. Anyone out there ever dealt with this before?

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  • Connect two daemons in python

    - by Simon
    What is the best way to connect two daemons in Python? I have daemon A and B. I'd like to receive data generated by B in A's module (maybe bidirectional). Both daemons support plugins, so I'd like to shut communication in plugins. What's the best and cross-platform way to do that? I know few mechanisms from low-level solutions - shared memory (C/C++), linux pipe, sockets (TCP/UDP), etc. and few high-level - queue (JMS, Rabbit), RPC. Both daemons should run on the same host, but obviously better approach is to abstract from connection type. What are typical solutions/libraries in python? I'm looking for an elegant and lightweight solution. I don't need external server, just two processes talking with each other. What should I use in python to do that?

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  • How can one describe a rock-paper-scissors relationship between 3 items?

    - by Madara Uchiha
    Let's say I have the following structure: abstract class Hand {} class Rock extends Hand {} class Paper extends Hand {} class Scissors extends Hand {} The goal is to make a function (or a method) Hand::compareHands(Hand $hand1, Hand $hand2), which would return the winning hand in a rock-paper-scissors match. That would be very easy with a bunch of ifs, but the point is to have a more robust structure, that's relying on polymorphism rather than on procedural code. P.S. this is done in actual production code, if someone is asking. This isn't some sort of challenge or homework. (It's not really rock-paper-scissors, but you get the point).

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  • designing multi module J2EE application

    - by user728947
    Might be my question is abstract or out of context, but i am asking here since i have little idea how this happens. I am wondering how big application/ platform break down there application in to multiple module and how they able to manage modules dependencies. For example in some E-commerce application they tend to break down it in various modules like pricing,promotions,shipping.import/export and many more. when we develop those application we hardly think about the underlying modules and how they have been designed to provides functionalists. Most of those module are not web-applications but are standalone module and not deployed in the web-app as jar files. can any one help me to understand how they break up things or is there any standard way to do this.any help/resources to get insight will really be helpful

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  • Why is the base class being called?

    - by oneBelizean
    I'm new to c# so bare with me. But here's my situation. interface Icontainer{ string name(); } abstract class fuzzyContainer : Icontainer{ string name(){ return "Fuzzy Container"; } } class specialContainer: fuzzyContainer{ string name(){ return base.name() + " Special Container"; } } Icontainer cont = new SpecialContainer(); cont.name(); // I expected "Fuzzy Container Special Container" as the output. When I run my code as described above the output is simply "Fuzzy Container". What am i missing here? Is there a better way to get the desired results?

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  • Receive messages for derived types in MVVMLight

    - by Hrvoje
    Shouldn't this test pass: [TestMethod] public void derived_message_subscription() { bool handled = false; Messenger.Default.Register<GenericMessage<baseClass>>(this, true, (msg) => handled = true); Messenger.Default.Send(new GenericMessage<testClass>(new testClass())); Assert.IsTrue(handled); } public abstract class baseClass { } public class testClass : baseClass { } I have to receive all messages for classes that inherits from one base class. MVVMLight has bool property receiveDerivedMessagesToo in Register method, but it seems to me that it isn't working.

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  • Pure virtual destructor in interface

    - by ALOR
    Hello all. Here is my problem. I'm making C++ dll, which extensively relies on instance object exports. So i return my actual instances as a pointers to interface through some exported factory method. Interfaces i use are purely virtual, to avoid linking problame. So i need a pure virtual destructor too, and i implemented one (with empty body, as i googled it). All compiles perfectly well, except... I can't see, if the actual destructors are called or not - because when i added some std::cout << "hello destructor"; i never get to see it. I have some explicit "delete obj", that's not the problem. Am i missing something? Is there another way to delete my object through interface?

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  • Rails architecture questions

    - by justinbach
    I'm building a Rails site that, among other things, allows users to build their own recipe repository. Recipes are entered either manually or via a link to another site (think epicurious, cooks.com, etc). I'm writing scripts that will scrape a recipe from these sites given a link from a user, and so far (legal issues notwithstanding) that part isn't giving me any trouble. However, I'm not sure where to put the code that I'm writing for these scraper scripts. My first thought was to put it in the recipes model, but it seems a bit too involved to go there; would a library or a helper be more appropriate? Also, as I mentioned, I'm building several different scrapers for different food websites. It seems to me that the elegant way to do this would be to define an interface (or abstract base class) that determines a set of methods for constructing a recipe object given a link, but I'm not sure what the best approach would be here, either. How might I build out these OO relationships, and where should the code go?

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  • System.ServiceModel.Channels.MessageHeader Error

    - by user220511
    I'm trying to get the following to work on my machine but I get an error (Cannot create an instance of the abstract class or interface 'System.ServiceModel.Channels.MessageHeader') using System; using System.IO; using System.Reflection; namespace com.mycompanyname.business { /// /// Summary description for SessionCreateRQClient. /// class SessionCreateRQClient { /// /// The main entry point. /// [STAThread] static void Main(string[] args) { try { // Set user information, including security credentials and the IPCC. string username = "user"; string password = "password"; string ipcc = "IPCC"; string domain = "DEFAULT"; string temp = Environment.GetEnvironmentVariable("tmp"); // Get temp directory string PropsFileName = temp + "/session.properties"; // Define dir and file name DateTime dt = DateTime.UtcNow; string tstamp = dt.ToString("s") + "Z"; //Create the message header and provide the conversation ID. MessageHeader msgHeader = new MessageHeader(); msgHeader.ConversationId = "TestSession"; // Set the ConversationId From from = new From(); PartyId fromPartyId = new PartyId(); PartyId[] fromPartyIdArr = new PartyId[1]; fromPartyId.Value = "WebServiceClient"; fromPartyIdArr[0] = fromPartyId; from.PartyId = fromPartyIdArr; msgHeader.From = from; To to = new To(); PartyId toPartyId = new PartyId(); PartyId[] toPartyIdArr = new PartyId[1]; toPartyId.Value = "WebServiceSupplier"; toPartyIdArr[0] = toPartyId; to.PartyId = toPartyIdArr; msgHeader.To = to; //Add the value for eb:CPAId, which is the IPCC. //Add the value for the action code of this Web service, SessionCreateRQ. msgHeader.CPAId = ipcc; msgHeader.Action = "SessionCreateRQ"; Service service = new Service(); service.Value = "SessionCreate"; msgHeader.Service = service; MessageData msgData = new MessageData(); msgData.MessageId = "mid:[email protected]"; msgData.Timestamp = tstamp; msgHeader.MessageData = msgData; Security security = new Security(); SecurityUsernameToken securityUserToken = new SecurityUsernameToken(); securityUserToken.Username = username; securityUserToken.Password = password; securityUserToken.Organization = ipcc; securityUserToken.Domain = domain; security.UsernameToken = securityUserToken; SessionCreateRQ req = new SessionCreateRQ(); SessionCreateRQPOS pos = new SessionCreateRQPOS(); SessionCreateRQPOSSource source = new SessionCreateRQPOSSource(); source.PseudoCityCode = ipcc; pos.Source = source; req.POS = pos; SessionCreateRQService serviceObj = new SessionCreateRQService(); serviceObj.MessageHeaderValue = msgHeader; serviceObj.SecurityValue = security; SessionCreateRS resp = serviceObj.SessionCreateRQ(req); // Send the request if (resp.Errors != null && resp.Errors.Error != null) { Console.WriteLine("Error : " + resp.Errors.Error.ErrorInfo.Message); } else { msgHeader = serviceObj.MessageHeaderValue; security = serviceObj.SecurityValue; Console.WriteLine("**********************************************"); Console.WriteLine("Response of SessionCreateRQ service"); Console.WriteLine("BinarySecurityToken returned : " + security.BinarySecurityToken); Console.WriteLine("**********************************************"); string ConvIdLine = "convid="+msgHeader.ConversationId; // ConversationId to a string string TokenLine = "securitytoken="+security.BinarySecurityToken; // BinarySecurityToken to a string string ipccLine = "ipcc="+ipcc; // IPCC to a string File.Delete(PropsFileName); // Clean up TextWriter tw = new StreamWriter(PropsFileName); // Create & open the file tw.WriteLine(DateTime.Now); // Write the date for reference tw.WriteLine(TokenLine); // Write the BinarySecurityToken tw.WriteLine(ConvIdLine); // Write the ConversationId tw.WriteLine(ipccLine); // Write the IPCC tw.Close(); //Console.Read(); } } catch(Exception e) { Console.WriteLine("Exception Message : " + e.Message ); Console.WriteLine("Exception Stack Trace : " + e.StackTrace); Console.Read(); } } } } I have added the reference System.ServiceModel and the lines: using System.ServiceModel; using System.ServiceModel.Channels; but I continue to get that error when trying to compile -- "Cannot create an instance of the abstract class or interface 'System.ServiceModel.Channels.MessageHeader'" I am using Microsoft Visual Studio 2008 Version 9.0.21022.8 RTM Microsoft .NET Framework Version 3.5 SP1 Professional Edition Is there another reference I have to add? Or a dll to move over? I wonder was the code above written for Framework 2.0 only? Thanks for your help.

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