如何解决VB.NET:如何处理变量类型参数和返回值?
| 是否可以替换这两个功能Function f1 (s As String) As class1()
Dim a() As String = Split(s)
Dim b(UBound(a)) As class1
For i As Integer = 0 To UBound(a)
b(i) = New class1(a(i))
Next
f1 = b
End Function
和
Function f2 (s As String) As class2()
Dim a() As String = Split(s)
Dim b(UBound(a)) As class2
For i As Integer = 0 To UBound(a)
b(i) = New class2(a(i))
Next
f2 = b
End Function
具有类似的通用功能
Function fGeneric (s As String,T As Type) As T()
Dim a() As String = Split(s)
Dim b(UBound(a)) As T
For i As Integer = 0 To UBound(a)
b(i) = New T(a(i))
Next
fGeneric = b
End Function
?
解
Class class1
Private _Name As String
Public ReadOnly Property Name As String
Get
Name = _Name
End Get
End Property
Sub New(s As String)
_Name = s
End Sub
End Class
Function fGeneric(Of T) (s As String) As IEnumerable(Of T)
Dim a() As String = Split(s)
Dim b(UBound(a)) As T
For i As Integer = 0 To UBound(a)
b(i) = GetType(T).InvokeMember( _
Nothing,_
BindingFlags.DeclaredOnly Or _
BindingFlags.Public Or _
BindingFlags.NonPublic Or _
BindingFlags.Instance Or _
BindingFlags.CreateInstance,_
Nothing,_
New Object(){a(i)} _
)
Next
fGeneric = b
End Function
Response.Write(fGeneric(Of class1)(\"a b c\")(1).Name)
输出b
解决方法
Function fGeneric(Of T) (ByVal s As String,ByVal createT As Func(Of String,T)) As IEnumerable(Of T)
Return Split(s).Select(Function(a) createT(a))
End Function
这样称呼它
fGeneric(Of class1)(\"some,string,value\",Function(a) Return New class1(a))
,正如@Joel指出的那样,可以使用linq很好地解决此问题,但为了接近@ ic3b3rg的问题,语法应为:
Function fGeneric(Of T As New) (s As String,createT As Func(Of String,T)) As T()
Dim a() As String = Split(s)
Dim b(UBound(a)) As T
For i As Integer = 0 To UBound(a)
b(i) = createT(a(i))
Next
fGeneric = b
End Function
fGeneric(Of class1)(\"some,Function(a) Return New class1(a))
编辑
仔细研究一下,我认为这不会奏效,因为我们从来没有说过可以从10英镑中构造出9英镑。我们只说过可以用new
创建T
。我不知道如何解决...欢迎任何建议(随时进行编辑)。
,看一下思考。我认为它可以帮助您获得与示例更紧密相关的结果。
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