如何检测何时可选的ByRef参数未被传递

我试图检测一个opational参数是否通过，但由于某些原因，所有常用函数（IsMissing（）/ IsEmpty（）/ IsNull（））总是返回false。

这就是我想要的：

Public Sub SetValue(Key As String, Optional ByRef ws As Worksheet) If IsMissing(ws) Or IsEmpty(ws) Or IsNull(ws) Then ws = ThisWorkbook.Sheets(SheetName) End If 

我也尝试将ws设置为Nothing或Null，但结果是一样的：

 Public Sub SetValue(Key As String, Optional ByRef ws As Worksheet = Nothing) If IsMissing(ws) Or IsEmpty(ws) Or IsNull(ws) Then ws = ThisWorkbook.Sheets(SheetName) End If 

任何想法为什么这可能会发生？

Answer 1

尝试is nothing

 Private Sub CommandButton1_Click() Dim ws As Excel.Worksheet Set ws = ActiveWorkbook.Sheets("sheet1") 'Call the sub both ways. SetValue "a" SetValue "a", ws End sub Public Sub SetValue(Key As String, Optional ByRef ws As Worksheet) If ws Is Nothing Then 'We got a sheet MsgBox "We got no sheet" End If If Not ws Is Nothing Then 'We got a sheet MsgBox ws.name MsgBox "We got a sheet" End If End sub 

Answer 2

build设是没有什么工作。 我在所有的参数中使用它。

 Public Sub SetValue(ByRef Key As String, _ Optional ByRef ws As Worksheet = Nothing) 'Make sure we have the object If ws Is Nothing Then Set ws = ThisWorkbook.Sheets(SheetName) End If End Sub 

希望这可以帮助。 🙂