自动检测被单独调用的参数 VS 为子例程调用

Question

我有三个子例程，有时连续运行，有时单独运行，但会使用相同的参数("TestNumber"(。我的原始代码如下所示：

Sub Main1()
    Dim TestNumber As String
        TestNumber = InputBox("Please enter TestNumber")
    ' Some codes running on TestNumber
    ' Prompt users whether to continue to Main2
    Dim Continue As String
        Continue = MsgBox("Continue to Main2?", vbYesNo)
        If Continue = vbYes Then
                Call Main2
            Else
        End If
End Sub
Sub Main2() ' Similar to Main1, just that it will prompt if user wants to continue to Main3
    Dim TestNumber As String
        TestNumber = InputBox("Please enter TestNumber")
    ' Some codes running on TestNumber
    Dim Continue As String
        Continue = MsgBox("Continue to Main3?"), vbYesNo)
        If Continue = vbYes Then
                Call Main3
            Else
        End If
End Sub
Sub Main3() ' The last call of the series
    Dim TestNumber As String
        TestNumber = InputBox("Please enter TestNumber")
    'Some codes running on TestNumber
End Sub

然后，我认为每次调用重新输入 TestNumber 有点麻烦和风险，所以我将我的代码更改为：

Sub Main1()
    Dim TestNumber As String
        TestNumber = InputBox("Please enter TestNumber")
    ' Some codes running on TestNumber
    ' Prompt users whether to continue to Main2
    Dim Continue As String
        Continue = MsgBox("Continue to Main2?", vbYesNo)
        If Continue = vbYes Then
                Call Main2(TestNumber)
            Else
        End If
End Sub
Sub Main2(TestNumber As String) ' Similar to Main1, just that it will prompt if user wants to continue to Main3
    If TestNumber = "" Then
            TestNumber = InputBox("Please enter TestNumber")
        Else
    End If
    ' Some codes running on TestNumber
    Dim Continue As String
        Continue = MsgBox("Continue to Main3?"), vbYesNo)
        If Continue = vbYes Then
                Call Main3(TestNumber)
            Else
        End If
End Sub
Sub Main3(TestNumber As String) ' The last call of the series
    If TestNumber = "" Then
            TestNumber = InputBox("Please enter TestNumber")
        Else
    End If
    ' Some codes running on TestNumber
End Sub

如果我从 Main3 开始一直工作到 Main1，这就可以了。但是如果我从 Main2 或 Main3 开始，两个脚本都无法运行。相反，系统会提示要运行的子例程。

有没有办法让子例程自动检测它是用参数调用还是单独调用？

Answer 1

您可以将参数标记为可选，并提供默认值，如下所示：

Sub Main2(Optional TestNumber As String = "")

或者，您可以将参数更改为变体，将其标记为可选，然后测试参数是否使用 IsMissing 提供，如下所示：

Sub Main2(Optional TestNumber As Variant)
If IsMissing(TestNumber) Then
    ' do stuff
Else
    ' do other stuff