使用子类实现接口 [英] Implementing an Interface with Child Classes

问题描述

我有以下接口：

Interface IViewModel
    ...
End Interface

Interface ISpecialViewModel
    Inherits IViewModel
    ...
End Interface

Interface IView
    WriteOnly Property MyViewModel As IViewModel
End Interface

以下是我的课程：

Class VerySpecialViewModel
    implements ISpecialViewModel
    ...
End Class

Class View
    Implements IView

    Public WriteOnly Property MyViewModel As VerySpecialViewModel Implements IView.MyViewModel 
        ...
    End Property
End Class

它告诉我'MyViewModel'无法实现'MyViewModel'，因为接口'IView'上没有匹配属性。

It tells me that 'MyViewModel' cannot implement 'MyViewModel' because there is no matching property on interface 'IView'.

推荐答案

Public Interface ISomething
    WriteOnly Property Prop As IParent
End Interface

您的类实现不满足该接口声明。请考虑以下情况：

That interface declaration isn't satisfied by your class implementation. Consider following situation:

还有另一个名为IChild2的接口：

There is another interface called IChild2:

Public Interface IChild2
    Inherits IParent
    ...
End Interface

根据 ISomething 界面，您应该能够将实现 IChild2 的类的实例分配到 Thing .Prop ，因为它继承了 IParent 。但你不能，因为 Thing.Prop 属性 IChild 类型和 IChild2 不继承 IChild

According to ISomething interface you should be able to assign instance of class implementing IChild2 into Thing.Prop, because it inherits IParent.But you can't, because Thing.Prop property is of IChild type and IChild2 does not inherits IChild

更新

Update

该解决方案怎么样？ ：

What about that solution:

Class ThingBase
    Implements ISomething

    Public WriteOnly Property Prop As IParent Implements ISomething.Prop
        Set(value As IParent)

        End Set
    End Property
End Class

Class Thing
    Inherits ThingBase

    Public Overloads WriteOnly Property Prop As IChild
        Set(value As IChild)
            MyBase.Prop = value
        End Set
    End Property
End Class

Update2

Update2

Interface IView(Of T As IViewModel)
    WriteOnly Property MyViewModel As T
End Interface

Class VerySpecialViewModel
    Implements ISpecialViewModel
End Class

Class View
    Implements IView(Of ISpecialViewModel)

    Public WriteOnly Property MyViewModel As ISpecialViewModel Implements IView(Of ISpecialViewModel).MyViewModel
        Set(value As ISpecialViewModel)

        End Set
    End Property
End Class

或

Class View
    Implements IView(Of VerySpecialViewModel)

    Public WriteOnly Property MyViewModel As VerySpecialViewModel Implements IView(Of VerySpecialViewModel).MyViewModel
        Set(value As VerySpecialViewModel)

        End Set
    End Property
End Class

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