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  • How do I run Eclipse using Oracle's new 1.7 JDK for the Mac?

    - by sanity
    I'm trying to get the new 1.7 JDK working with Eclipse (this is Oracle's official release). I don't mean just pointing Eclipse to it so you can use it in projects, this works fine, but actually making Eclipse run using the 1.7 JVM. I've moved the new JVM to the top of the list in Java Preferences, but Eclipse still starts with 1.6. If I disable 1.6 in Java Preferences I get a dialog immediately after I double-click on Eclipse saying "Failed to create the Java Virtual Machine". edit: I added the following to my eclipse.ini just before the -vmargs: -vm /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/bin/java Yet in the Eclipse installation details dialog I still see: java.runtime.version=1.6.0_31-b04-415-11M3646 edit 2: here are the contents of my eclipse.ini file: https://gist.github.com/2512578

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  • Invoking static methods containing Generic Parameters using Reflection.

    - by AJP
    While executing the following code i gets this error "Late bound operations cannot be performed on types or methods for which ContainsGenericParameters is true." class Program { static void Main(string[] args) { MethodInfo MI = typeof(MyClass).GetMethod("TestProc"); MI.MakeGenericMethod(new [] {typeof(string)}); MI.Invoke(null, new [] {"Hello"}); } } class MyClass { public static void TestProc<T>(T prefix) { Console.WriteLine("Hello"); } } Please help.

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  • Operator as and generic classes

    - by abatishchev
    I'm writing .NET On-the-Fly compiler for CLR scripting and want execution method make generic acceptable: object Execute() { return type.InvokeMember(..); } T Execute<T>() { return Execute() as T; /* doesn't work: The type parameter 'T' cannot be used with the 'as' operator because it does not have a class type constraint nor a 'class' constraint */ // also neither typeof(T) not T.GetType(), so on are possible return (T) Execute(); // ok } But I think operator as will be very useful: if result type isn't T method will return null, instead of an exception! Is it possible to do?

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  • Generic Func<> as parameter to base method

    - by WestDiscGolf
    I might be losing the plot, but I hope someone can point me in the right direction. What am I trying to do? I'm trying to write some base methods which take Func< and Action so that these methods handle all of the exception handling etc. so its not repeated all over the place but allow the derived classes to specify what actions it wants to execute. So far this is the base class. public abstract class ServiceBase<T> { protected T Settings { get; set; } protected ServiceBase(T setting) { Settings = setting; } public void ExecAction(Action action) { try { action(); } catch (Exception exception) { throw new Exception(exception.Message); } } public TResult ExecFunc<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function) { try { /* what goes here?! */ } catch (Exception exception) { throw new Exception(exception.Message); } } } I want to execute an Action in the following way in the derived class (this seems to work): public void Delete(string application, string key) { ExecAction(() => Settings.Delete(application, key)); } And I want to execute a Func in a similar way in the derived class but for the life of me I can't seem to workout what to put in the base class. I want to be able to call it in the following way (if possible): public object Get(string application, string key, int? expiration) { return ExecFunc(() => Settings.Get(application, key, expiration)); } Am I thinking too crazy or is this possible? Thanks in advance for all the help.

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  • Force calling the derived class implementation within a generic function in C#?

    - by Adam Hardy
    Ok so I'm currently working with a set of classes that I don't have control over in some pretty generic functions using these objects. Instead of writing literally tens of functions that essentially do the same thing for each class I decided to use a generic function instead. Now the classes I'm dealing with are a little weird in that the derived classes share many of the same properties but the base class that they are derived from doesn't. One such property example is .Parent which exists on a huge number of derived classes but not on the base class and it is this property that I need to use. For ease of understanding I've created a small example as follows: class StandardBaseClass {} // These are simulating the SMO objects class StandardDerivedClass : StandardBaseClass { public object Parent { get; set; } } static class Extensions { public static object GetParent(this StandardDerivedClass sdc) { return sdc.Parent; } public static object GetParent(this StandardBaseClass sbc) { throw new NotImplementedException("StandardBaseClass does not contain a property Parent"); } // This is the Generic function I'm trying to write and need the Parent property. public static void DoSomething<T>(T foo) where T : StandardBaseClass { object Parent = ((T)foo).GetParent(); } } In the above example calling DoSomething() will throw the NotImplemented Exception in the base class's implementation of GetParent(), even though I'm forcing the cast to T which is a StandardDerivedClass. This is contrary to other casting behaviour where by downcasting will force the use of the base class's implementation. I see this behaviour as a bug. Has anyone else out there encountered this?

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  • Html.Editor() helper in ASP.NET MVC 3 does not work as expected with array in model

    - by SlimShaggy
    In my ASP.NET MVC 3 application I have classes like the following: public class Localization<T> { public int VersionID { get; set; } public T Value { get; set; } ... } public class Localizable<T> { public Localization<T>[] Name { get; set; } ... } Then, I have the following view: @model dynamic ... @for (int i = 0; i < VersionCount; i++) { ... @Html.Editor(string.Format("Name[{0}.Value", i)) ... } Now, when I display this view, passing a subclass of Localizable<string> as the model, the textboxes for the strings are rendered, but they are empty. If I replace @Html.Editor(string.Format("Name[{0}.Value", i)) with @InputExtensions.TextBox(Html, string.Format("Name[{0}].Value", i), Model.Name[i].Value), the textboxes are correctly filled with values from the model. However, using TextBox instead of Editor is not an option for me, because I want to use different editor templates for different types of T. So, what am I doing wrong, or is it a bug in MVC, and is there any workaround?

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  • Delphi 2010 - Why can't I declare an abstract method with a generic type parameter?

    - by James
    I am trying to do the following in Delphi 2010: TDataConverter = class abstract public function Convert<T>(const AData: T): string; virtual; abstract; end; However, I keep getting the following compiler error: E2533 Virtual, dynamic and message methods cannot have type parameters I don't quite understand the reason why I can't do this. I can do this in C# e.g. public abstract class DataConverter { public abstract string Convert<T>(T data); } Anyone know the reasoning behind this?

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  • Why can't I enforce derived classes to have parameterless constructors?

    - by FrisbeeBen
    I am trying to do the following: public class foo<T> where T : bar, new() { public foo() { _t = new T(); } private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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  • How to use method hiding (new) with generic constrained class

    - by ongle
    I have a container class that has a generic parameter which is constrained to some base class. The type supplied to the generic is a sub of the base class constraint. The sub class uses method hiding (new) to change the behavior of a method from the base class (no, I can't make it virtual as it is not my code). My problem is that the 'new' methods do not get called, the compiler seems to consider the supplied type to be the base class, not the sub, as if I had upcast it to the base. Clearly I am misunderstanding something fundamental here. I thought that the generic where T: xxx was a constraint, not an upcast type. This sample code basically demonstrates what I'm talking about. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace GenericPartialTest { class ContextBase { public string GetValue() { return "I am Context Base: " + this.GetType().Name; } public string GetOtherValue() { return "I am Context Base: " + this.GetType().Name; } } partial class ContextSub : ContextBase { public new string GetValue() { return "I am Context Sub: " + this.GetType().Name; } } partial class ContextSub { public new string GetOtherValue() { return "I am Context Sub: " + this.GetType().Name; } } class Container<T> where T: ContextBase, new() { private T _context = new T(); public string GetValue() { return this._context.GetValue(); } public string GetOtherValue() { return this._context.GetOtherValue(); } } class Program { static void Main(string[] args) { Console.WriteLine("Simple"); ContextBase myBase = new ContextBase(); ContextSub mySub = new ContextSub(); Console.WriteLine(myBase.GetValue()); Console.WriteLine(myBase.GetOtherValue()); Console.WriteLine(mySub.GetValue()); Console.WriteLine(mySub.GetOtherValue()); Console.WriteLine("Generic Container"); Container<ContextBase> myContainerBase = new Container<ContextBase>(); Container<ContextSub> myContainerSub = new Container<ContextSub>(); Console.WriteLine(myContainerBase.GetValue()); Console.WriteLine(myContainerBase.GetOtherValue()); Console.WriteLine(myContainerSub.GetValue()); Console.WriteLine(myContainerSub.GetOtherValue()); Console.ReadKey(); } } }

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  • Generic delegate instances

    - by Luc C
    I wonder if C# (or the underlying .NET framework) supports some kind of "generic delegate instances": that is a delegate instance that still has an unresolved type parameter, to be resolved at the time the delegate is invoked (not at the time the delegate is created). I suspect this isn't possible, but I'm asking it anyway... Here is an example of what I'd like to do, with some "???" inserted in places where the C# syntax seems to be unavailable for what I want. (Obviously this code doesn't compile) class Foo { public T Factory<T>(string name) { // implementation omitted } } class Test { public void TestMethod() { Foo foo = new Foo(); ??? magic = foo.Factory; // No type argument given here yet to Factory! // What would the '???' be here (other than 'var' :) )? string aString = magic<string>("name 1"); // type provided on call int anInt = magic<int>("name 2"); // another type provided on another call // Note the underlying calls work perfectly fine, these work, but i'd like to expose // the generic method as a delegate. string aString2 = foo.Factory<string>("name 1"); int anInt2 = foo.Factory<int>("name 2"); } } Is there a way to actually do something like this in C#? If not, is that a limitation in the language, or is it in the .NET framework?

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  • How to check if TypeIdenitifier(T) is an Object?

    - by John
    I'm creating a generic list class that has a member of type Array(Array of ). The problem is the class descruction,because the class is supposed to be used for types from byte to types inheriting TObject. Specifically: destructor Destroy; var elem:T; begin /*if(T is Tobject) then //Check if T inherits TObject {Compiler error!} for elem in FData do TObject(elem).Free;*/ // do not know how to do it SetLength(FItems,0); //FItems : Array of T inherited Destroy; end; How do I check if T is TObject so I can free every member if the typeidenitifier is a class,for example?

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  • Common type for generic classes of different types

    - by DinGODzilla
    I have (for example) Dictionary of different generic types (d1, d2, d3, d4) and I want to store them in something var d1 = new Dictionary<int, string>(); var d2 = new Dictionary<int, long>(); var d3 = new Dictionary<DateTime, bool>(); var d4 = new Dictionary<string, object>(); var something = ??? //new List<object> {d1, d2, d3, d4}; Is there any other way how to store that in something with common denominator different than object? Thanks :-)

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  • scala 2.8 CanBuildFrom

    - by oxbow_lakes
    Following on from another question I asked, I wanted to understand a bit more about the Scala method TraversableLike[A].map whose signature is as follows: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That Notice a few things about this method: it takes a function turning each A in the traversable into a B it returns That and takes an implicit argument of type CanBuildFrom[Repr, B, That] I can call this as follows: > val s: Set[Int] = List("Paris", "London").map(_.length) s: Set[Int] Set(5,6) What I cannot quite grasp is how the fact that That is bound to B (i.e. it is some collection of B's) is being enforced by the compiler. The type parameters look to be independent in both the signature above and in the signature of the trait CanBuildFrom itself: trait CanBuildFrom[-From, -Elem, +To] How is the scala compiler ensuring that That cannot be forced into something which does not make sense? > val s: Set[String] = List("Paris", "London").map(_.length) //will not compile EDIT - this question of course boils down to: How does the compiler decide what implicit CanBuildFrom objects are in scope for the call?

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  • Overriding inherited generic methods

    - by jess
    I have this code in base class protected virtual bool HasAnyStuff<TObject>(TObject obj) where TObject:class { return false; } In child class I am overriding protected override bool HasAnyStuff<Customer>(Customer obj) { //some stuff if Customer.sth etc return false; } I am getting this error '''Type parameter declaration must be an identifier not a type''' What is it I am doing wrong here?

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  • Is it possible in Scala to force the caller to specify a type parameter for a polymorphic method ?

    - by Alex Kravets
    //API class Node class Person extends Node object Finder { def find[T <: Node](name: String): T = doFind(name).asInstanceOf[T] } //Call site (correct) val person = find[Person]("joe") //Call site (dies with a ClassCast inside b/c inferred type is Nothing) val person = find("joe") In the code above the client site "forgot" to specify the type parameter, as the API writer I want that to mean "just return Node". Is there any way to define a generic method (not a class) to achieve this (or equivalent). Note: using a manifest inside the implementation to do the cast if (manifest != scala.reflect.Manifest.Nothing) won't compile ... I have a nagging feeling that some Scala Wizard knows how to use Predef.<:< for this :-) Ideas ?

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  • unable to pas derived List<>

    - by Tarscher
    Hi all, I have class A {} class B : A {} I also have a method that expects a List parameter void AMethod(List<A> parameter) {} Why can't I List<B> bs = new List<B>(); AMethod(bs); And secondly what is the most elegant way to make this work? regards

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  • [C#] How do I make hierarchy of objects from two alternating classes?

    - by Millicent
    Here's the scenario: I have two classes ("Page" and "Field"), that are descended from a common class ("Pield"). They represent tags in an XML file and are in the following hierarchy: <page> <field> <page> ... </page> ... </field> ... </page> I.e.: Page and Field objects are in a hierarchy of alternating type (there may be more than one Page or Field to each rung of the hierarchy). Every Field and Page object has a parent property, which points to the respective parent object of the other type. This is not a problem unless the parent-child mechanism is controlled by the base class (Pield), which is shared by the two descended classes (Page and Field). Here is one try, that fails at the line "Pield child = new Pield(pchild, this);": class Pield<T> { private T _pield_parent; ... private void get_children() { ... Pield<Page> child = new Pield<Page>(pchild, this); ... } ... } class Page : Pield<Field> { ... } class Field : Pield<Page> { ... } Any ideas about how to solve this elegantly? Best, Millicent

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  • Generic Dictionary - Getting Conversion Error

    - by pm_2
    The following code is giving me an error: // GetDirectoryList() returns Dictionary<string, DirectoryInfo> Dictionary<string, DirectoryInfo> myDirectoryList = GetDirectoryList(); // The following line gives a compile error foreach (Dictionary<string, DirectoryInfo> eachItem in myDirectoryList) The error it gives is as follows: Cannot convert type 'System.Collections.Generic.KeyValuePair<string,System.IO.DirectoryInfo>' to 'System.Collections.Generic.Dictionary<string,System.IO.DirectoryInfo>’ My question is: why is it trying to perform this conversion? Can I not use a foreach loop on this type of object?

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  • What's the most efficient way to combine two List(Of String)?

    - by Jason Towne
    Let's say I've got: Dim los1 as New List(Of String) los1.Add("Some value") Dim los2 as New List(Of String) los2.Add("More values") What would be the most efficient way to combine the two into a single List(Of String)? Edit: While I'm loving the solutions everyone has provided so far, I probably should also mention I'm stuck using the .NET 2.0 framework. Any other suggestions?

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  • Why can't these generic type parameters be inferred?

    - by Jon M
    Given the following interfaces/classes: public interface IRequest<TResponse> { } public interface IHandler<TRequest, TResponse> where TRequest : IRequest<TResponse> { TResponse Handle(TRequest request); } public class HandlingService { public TResponse Handle<TRequest, TResponse>(TRequest request) where TRequest : IRequest<TResponse> { var handler = container.GetInstance<IHandler<TRequest, TResponse>>(); return handler.Handle(request); } } public class CustomerResponse { public Customer Customer { get; set; } } public class GetCustomerByIdRequest : IRequest<CustomerResponse> { public int CustomerId { get; set; } } Why can't the compiler infer the correct types, if I try and write something like the following: var service = new HandlingService(); var request = new GetCustomerByIdRequest { CustomerId = 1234 }; var response = service.Handle(request); // Shouldn't this know that response is going to be CustomerResponse? I just get the 'type arguments cannot be inferred' message. Is this a limitation with generic type inference in general, or is there a way to make this work?

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  • Why isn't the new() generic constraint satisfied by a class with optional parameters in the construc

    - by Joshua Flanagan
    The following code fails to compile, producing a "Widget must be a non-abstract type with a public parameterless constructor" error. I would think that the compiler has all of the information it needs. Is this a bug? An oversight? Or is there some scenario where this would not be valid? public class Factory<T> where T : new() { public T Build() { return new T(); } } public class Widget { public Widget(string name = "foo") { Name = name; } public string Name { get; set; } } public class Program { public static void Main() { var widget = new Widget(); // this is valid var factory = new Factory<Widget>(); // compiler error } }

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  • Why does this static factory method involving implied generic types, work?

    - by Cheeso
    Consider public class Tuple<T1, T2> { public Tuple(T1 v1, T2 v2) { V1 = v1; V2 = v2; } public T1 V1 { get; set; } public T2 V2 { get; set; } } public static class Tuple { // MAGIC!! public static Tuple<T1, T2> New<T1, T2>(T1 v1, T2 v2) { return new Tuple<T1, T2>(v1, v2); } } Why does the part labeled "MAGIC" in the above work? It allows syntax like Tuple.New(1, "2") instead of new Tuple<int, string>(1, "2"), but ... how and why? Why do I not need Tuple.New<int,string>(1, "2") ??

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  • How can I define multiple types with the same name and different type parameters using Reflection Em

    - by wawa
    How can I generate types like these using the System.Reflection.Emit libraries: public class Test<T> {} public class Test<T1, T2> {} When I call ModuleBuilder.DefineType(string) with the second type declaration, I get an exception because there is already another type in the module with the same name (I've already defined the type parameter on the first type). Any ideas?

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