generics

问题 I made a custom TObjectList descendant designed to hold subclasses of a base object class. It looks something like this: interface TMyDataList<T: TBaseDatafile> = class(TObjectList<TBaseDatafile>) public constructor Create; procedure upload(db: TDataSet); end; implementation constructor TMyDataList<T>.Create; begin inherited Create(true); self.Add(T.Create); end; I want each new list to start out with one blank object in it. It's pretty simple, right? But the compiler doesn't like it. It says

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: Structs, Interfaces and Boxing From the MSDN: http://msdn.microsoft.com/en-us/library/yz2be5wk.aspx Boxing is the process of converting a value type to the type object or to any interface type implemented by this value type. But what about generic interfaces? For example, int derives from both IComparable and IComparable<int> . Let's say I have the following code: void foo(IComparable value) { /* etc. */ } void

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: Structs, Interfaces and Boxing From the MSDN: http://msdn.microsoft.com/en-us/library/yz2be5wk.aspx Boxing is the process of converting a value type to the type object or to any interface type implemented by this value type. But what about generic interfaces? For example, int derives from both IComparable and IComparable<int> . Let's say I have the following code: void foo(IComparable value) { /* etc. */ } void

问题 How do I call Class.forName() when the result is a generic type? Usually I can use asSubclass() , but here the only way I see to do it is a cast, which kindof sticks out & bugs me when everything else is nicely typed with generics. The scenario goes something like this: There is a .jar with one entry point main class that has a main() . It takes an option of a classname (and some others, irrelevant here). The class given implements Callable<Integer> . This class is loaded, inited & launched.

问题 I am failing to see why my attempt to cast to a generic base class is not working. The basic structure of the code is as follows. interface ICmd { } class Context { } class Cmd<TContext> : ICmd where TContext : Context { } class MyContext : Context { } class MyCmd : Cmd<MyContext> { } So now I have an instance of ICmd and want to cast it to Cmd as follows var base = cmd as Cmd<Context> base is always null after this line is executed. changing cast to be specific for the context only and it

问题 I am writing some classes using Generics but I can't find a solution for the class SolutionsSubset and so I a getting the error "type parameter S is not within its bound". I have read previous questions about the same error but I can't solve it for my case. Could anybody help me to improve my knowledge about generics? Any reference to a good book (I can find in google a lot of information but if someone can reccommend a book, tutorial, etc. will be welcome). Although I tried to keep in mind

问题 From this Oracle Java tutorial: The WildcardError example produces a capture error when compiled: public class WildcardError { void foo(List<?> i) { i.set(0, i.get(0)); } } After this error demonstration, they fix the problem by using a helper method: public class WildcardFixed { void foo(List<?> i) { fooHelper(i); } // Helper method created so that the wildcard can be captured // through type inference. private <T> void fooHelper(List<T> l) { l.set(0, l.get(0)); } } First, they say that the

问题 I have defined one interface and one class: public interface IRepository<T> { } public class RoleRepository:IRepository<Domain_RoleInfo> { } Inject here: public RoleService { [Inject] public RoleService(IRepository<Domain_RoleInfo> rep) { _roleRep=rep; } } How can I perform Dependency Injection With Ninject,say how to bind? I have written a helper class as below, it works fine with non-generic interface.but how to refactor it support generic interface as above? public class

问题 I am extending a base class (one which I do not control) in Swift. I want to provide a class function for creating an instance typed to a subclass. A generic function is required. However, an implementation like the one below does not return the expected subclass type. class Calculator { func showKind() { println("regular") } } class ScientificCalculator: Calculator { let model: String = "HP-15C" override func showKind() { println("scientific") } } extension Calculator { class func create<T

问题 I am extending a base class (one which I do not control) in Swift. I want to provide a class function for creating an instance typed to a subclass. A generic function is required. However, an implementation like the one below does not return the expected subclass type. class Calculator { func showKind() { println("regular") } } class ScientificCalculator: Calculator { let model: String = "HP-15C" override func showKind() { println("scientific") } } extension Calculator { class func create<T