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在不同的泛型实例上实现相同的接口

generics interface f#

Gabriel · 技术社区 · 16 年前

interface IFoo<T> { void Foo(T x); }

class Bar : IFoo<int>, IFoo<float>
{
    public void Foo(int x) { }
    public void Foo(float y) { }
}

type IFoo<'a> = abstract member Foo : 'a -> unit

type Bar() =
    interface IFoo<int> with 
        [<OverloadID("int")>]
        member this.Foo x = ()

    interface IFoo<float> with 
        [<OverloadID("float")>]
        member this.Foo x = ()

'IFoo<float>' 和 'IFoo<int>' 。此版本的F#不允许这样做。

我找不到 discussion of this issue

2 回复 | 直到 13 年前

Abel 10 年前

.特点 has been planned 并且至少部分地(见注释)在F#4.0中实现。

编辑

public interface IG<T>
{
    void F(T x);
}
public class CIG : IG<int>, IG<string>
{
    public void F(int x) { Console.WriteLine("int"); }
    public void F(string x) { Console.WriteLine("str"); }
}

let cig = new CIG()
let idunno = cig :> IG<_>  // type IG<int>, guess just picks 'first' interface?
let ii = cig :> IG<int>    // works
ii.F(42)                   // prints "int"
let is = cig :> IG<string> // works
is.F("foo")                // prints "str"

所以这就是通常在这个“边界”上发生的事情,F#可以很好地使用这些东西,即使你不能在语言中编写相同的东西。

Tom DeMille 10 年前

有一种合理但不优雅的方法,为每个接口创建一个新类型。这里是一个从ESB(nSvcBus)消费多个事件的示例,它要求每个事件对应一个已实现的接口。下面的第一种类型包含泛型“处理程序”代码,其他类型只实现接口并调用泛型处理程序

type public nSvcBusEvents() = 

    member this.HandleEvents(msg:IEvent) = ()
        //handle messages ie: let json = JsonConvert.SerializeObject(msg)

type public ActionLoggedHandler() = 
    interface IHandleMessages<Events.ActionLoggedEvent> with
        member this.Handle(msg : ActionLoggedEvent) = 
            nSvcBusEvents().HandleEvents(msg)

type public ActionCompletedHandler() = 
    interface IHandleMessages<Events.ActionCompletedHandler> with
        member this.Handle(msg : ActionCompletedHandler) = 
            nSvcBusEvents().HandleEvents(msg)

type public ActionFailedHandler() =       
    interface IHandleMessages<Events.ActionFailedHandler> with
        member this.Handle(msg : ActionFailedHandler) = 
            nSvcBusEvents().HandleEvents(msg)

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