在這種情況下，使用僅在運行時才知道的型別的泛型有什么更好的選擇？

現在我只能將 Jumper 類用于“Something”型別的物件。我嘗試將它重寫為泛型類，但在從我的 SomeForm 類中實際呼叫它時遇到了困難，因為“T”可能是我只在運行時才知道的幾種型別之一。我讀到這意味著我基本上是在與整個泛型語言設計作斗爭。

示例代碼是 VB，但我也可以使用 C# 答案。

問題：這可以用泛型重新設計嗎？或者在我的情況下，什么是泛型的更好替代品？

Public Class Jumper
    Private _enumeratorForwards As IEnumerator(Of Something)

    Public Sub JumpNext(functions As FunctionCombi)
        Forwards(functions.SelectorFunc)
    End Sub

    Private Iterator Function Forwards(selectorFunc As Func(Of Something, Boolean)) As IEnumerable(Of Something)

End Class

Public Class FunctionCombi
    Public Property SelectorFunc As Func(Of Something, Boolean)

    Sub New(_selectorFunc As Func(Of Something, Boolean))
        SelectorFunc = _selectorFunc
    End Sub

End Class

Public Class SomeForm

    'x and y would be different types
    Private _functionCombis As New Dictionary(Of SomeEnum, FunctionCombi) From {
                                                   {SomeEnum.A, New FunctionCombi(Function(x) RunSomeFunction(x)},
                                                   {SomeEnum.B, New FunctionCombi(Function(y) RunSomeOtherFunction(y))}

    Private Sub SomeHandler(sender as object, e as EventArgs)
        For i = 1 To [Enum].GetValues(GetType(SomeEnum)).Length

            'The type I would need here differs and I only know it at runtime

            Dim functionInfo As FunctionCombi = Nothing
            If Not _functionCombis.TryGetValue(i, functionInfo) Then Continue For
            Dim jumper As Jumper = sender.Tag(2)
        Next
    End Sub
End Class

uj5u.com熱心網友回復：

泛型型別很可能不是您需要的，因為它們是在compile time中解決的。對于要在運行時決議的不同型別，請使用介面。

如果一個人可以完全控制所涉及的型別，那只是意味著：定義一個介面并讓兩種型別都實作該介面。

Public Interface IOfficeObject
    ' any members that Shape and TextRange have in common
End Interface

Public Interface Shape
    Inherits IOfficeObject

    ' any members specific for Shape
End Interface

Public Interface TextRange
    Inherits IOfficeObject

    ' any members specific for TextRange
End Interface

然后Jumper只需與該介面對話，而不用關心底層實作。 Jumper 不應該關心那些基礎類，否則它將違背將兩個類放在同一個IEnumerator.

Public Class Jumper
    Private _enumeratorForwards As IEnumerator(Of IOfficeObject)

    ...
End Class

您沒有解釋什么Shape和TextRange（以及您可能感興趣的任何其他 MS 介面）有什么共同點，您也沒有解釋您的代碼將對這些物件采取什么樣的操作。這是一種恥辱，因為這意味著我必須用一些假設的例子來說明我的觀點。

讓我們假設Shape并TextRange有以下共同點：

• Application型別的屬性Application，類似于此
• 一個方法Copy，類似于這個

這使我的通用界面：

Public Interface IOfficeObject
    ReadOnly Property Application As Application
    Sub Copy()
End Interface

不幸的是，您無法控制Shapeand TextRange; 它們是微軟定義的介面。顯然，微軟并沒有費心去定義一個共同的介面來同時被Shape和繼承TextRange。我不知道為什么；我不熟悉這些界面或它們的歷史。這可能是一個疏忽，變成了遺產。

您可以使用配接器模式來解決該問題。

Public Class ShapeAdapter
    Implements IOfficeObject

    Private ReadOnly _shape As Shape

    Public Sub New(shape As Shape)
        _shape = shape
    End Sub

    Public ReadOnly Property Application As Application
        Get
            Return _shape.Application
        End Get
    End Property

    Public Sub Copy()
        _shape.Copy()
    End Sub

    ' Any other members, forwarding to _shape
End Class

Public Class TextRangeAdapter
    Implements IOfficeObject

    Private ReadOnly _textRange As TextRange

    Public Sub New(textRange As TextRange)
        _textRange = textRange
    End Sub

    Public ReadOnly Property Application As Application
        Get
            Return _textRange.Application
        End Get
    End Property

    Public Sub Copy()
        _textRange.Copy()
    End Sub

    ' Any other members, forwarding to _textRange
End Class

產生可列舉的物件涉及將每個物件包裝在其配接器類中。例子：

Dim listOfOfficeObjects As New List(Of IOfficeObject)
listOfOfficeObjects.Add(New ShapeAdapter(shape1))
listOfOfficeObjects.Add(New TextRangeAdapter(textRange1))
listOfOfficeObjects.Add(New ShapeAdapter(shape2))
listOfOfficeObjects.Add(New TextRangeAdapter(textRange2))

（如果您更喜歡工廠而不是 and 的顯式實體化ShapeAdapter，TextRangeAdapter那當然可以。）

Class Jumper will retrieve these adapters. Consumers will always be talking to these adapters, through interface IOfficeObject. In your own code sample, I recognize two consumers, but I'm sure there will be more in the solution you are working on.

Public Function RunSomeFunction(obj As IOfficeObject) As Boolean
    ' pulling whatever is necessary from IOfficeObject to come to a return value
End Function

Public Function RunSomeOtherFunction(obj As IOfficeObject) As Boolean
    ' likewise
End Function

If a consumer needs anything from Shape or TextRange that is not exposed by the interface and/or not implemented by the adapters, then that is something that needs to be fixed in the interface and the adapters. If it cannot be implemented by the adapters, then there is a flaw in your architecture.

標籤：C＃ VB.net 仿制药

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