Question

我的功能如下：

Public Shared Iterator Function MyFunction(ByVal param1 As String) _
As IEnumerable(Of FileInfo)
    ...
End Function

我想添加一个带有SAME参数 Type 但是更改返回 Type 的重载，如下所示：

Public Shared Iterator Function MyFunction(ByVal param1 As String) _
As IEnumerable(Of String)
    ...
End Function

可以在不更改param1类型的情况下完成吗？我考虑过在Function MyFunction(Of T)(ByVal param1 As String) As Ienumerable(Of T)这两个函数上添加 Type 参数，以期如下所示：

Dim collection As IEnumerable(Of String) = MyFunction(Of String)("")
Dim collection As IEnumerable(Of FileInfo) = MyFunction(Of FileInfo)("")

但要做到这一点，我还需要更改param1值的类型，我也看到了通过人为错误传递不同类型参数的缺点，例如调用函数作为{ {1}}然后在函数内添加意外类型参数的错误处理......似乎不是一种干净/安全的方法。

所以我明确地希望将Return MyFunction(Of Integer)("")用作 String ，相同的函数名，并在每个函数上返回不同的枚举，我完全知道一个返回<的函数strong>对象或者使用类型参数以这种方式搞乱，我不认为这是一个干净的解决方案：

param1

哪种方法可以解决这个问题呢？ ......这对我暴露的要求真的可行吗？

Answer 1

在这种情况下， de jure / facto 只是简单地重命名每个函数以反映返回类型。实际上，这是我推荐的唯一方法。

Public Shared Iterator Function GetStrings(ByVal param1 As String) As IEnumerable(Of String)
End Function

Public Shared Iterator Function GetFiles(ByVal param1 As String) As IEnumerable(Of FileInfo)
End Function

选项1

但如果你能接受一些含糊不清的警告，那么可以选择创建一个实现IEnumerable(T)的自定义返回类型。

Public Class MyFunctionIterator
    Implements IEnumerable, IEnumerable(Of String), IEnumerable(Of FileInfo)

    Friend Sub New(param1 As String)
        Me.param1 = param1
    End Sub

    Private param1 As String

    Public Iterator Function GetStrings() As IEnumerator(Of String) Implements IEnumerable(Of String).GetEnumerator
        For Each item As String In {"a", "b", "c", "d"}
            Yield item
        Next
    End Function

    Public Iterator Function GetFiles() As IEnumerator(Of FileInfo) Implements IEnumerable(Of FileInfo).GetEnumerator
        For Each name As String In Directory.GetFiles(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments))
            Yield New FileInfo(name)
        Next
    End Function

    Private Iterator Function GetEnumerator() As IEnumerator Implements IEnumerable.GetEnumerator
        Throw New NotSupportedException()
    End Function

End Class

的

Public Shared Function MyFunction(ByVal param1 As String) As MyFunctionIterator
    Return New MyFunctionIterator(param1)
End Function

<子>的用法

Dim collection1 As IEnumerable(Of String) = MyFunction("...") Dim collection2 As IEnumerable(Of FileInfo) = MyFunction("...") For Each s In collection1 Debug.Write(s & ", ") Next Debug.WriteLine("") For Each fi In collection2 Debug.Write(fi.Name & ", ") Next


a，b，c，d，
  desktop.ini，file1.txt，file2.txt，file3.txt，

选项2

如果您使用接口，则另一个选项是创建自定义返回类型并定义conversion operators。

Public Class MyFunctionResult Friend Sub New(param1 As String) Me.param1 = param1 End Sub Private param1 As String Public Function GetString() As String Return ("Hello " & Me.param1 & "!") End Function Public Shared Widening Operator CType(value As MyFunctionResult) As String Return value.GetString() End Operator Public Function GetFile() As FileInfo Return New FileInfo(Me.param1) End Function Public Shared Widening Operator CType(value As MyFunctionResult) As FileInfo Return value.GetFile() End Operator End Class

的

Public Shared Function MyFunction(ByVal param1 As String) As MyFunctionResult Return New MyFunctionResult(param1) End Function

<子>的用法

Dim s As String = MyFunction("Bjørn") Dim fi As FileInfo = MyFunction("C:\Users\bjorn\Documents\file1.txt") Debug.WriteLine(s) Debug.WriteLine(fi.Name)


你好Bjørn！
  FILE1.TXT

关于具有不同返回类型的函数重载的问题

1 个答案: