VBA功能可选参数 [英] VBA Function Optional parameters

问题描述

我多次调用特定的代码，因此我想使用可选参数. 我可以这样写:

I am calling a specific piece of code several times therefore I would like to use optional parameters. I can write something like:

Public Sub main()

strA = "A"

'Calling the function
CalculateMe (strA)

End Sub

Public Sub CalculateMe(strA As String)

    Set rs = DB.OpenRecordset("tbl_A")
    rs.MoveFirst
        Do Until rs.EOF
            If rs.Fields(0) = strA Then
                dblA = rs.fields(2).Value
            End If
            rs.MoveNext
        Loop
End Sub

如何更改功能以容纳1个以上的可选参数?

How can I change the function to hold more than 1 optional parameters?

类似的东西:

Public Sub main()
strA = "A"
strB = "B"

'Calling the function
CalculateMe (strA, strB)

more code
End Sub

Public Sub CalculateMe(Optional strA As String, Optional strB as String)

    Set rs = DB.OpenRecordset("tbl_A")
    rs.MoveFirst
        Do Until rs.EOF
            If rs.Fields(0).Value = strA And rs.Fields(1).Value = strB Then
                dblA = rs.Fields(2).Value
            End If
            rs.MoveNext
        Loop
End Sub

按照Pankaj Jaju的建议，我设法将其更改为:

Following Pankaj Jaju's advice, I have managed to have it run by changing it to:

Public Sub main()
strA = "A"
strB = "B"

'Calling the function
dblA = CalculateMe (strA, strB)

End Sub

Public Function CalculateMe(Optional ByVal strA As String, Optional ByVal strB as String)

Set rs = DB.OpenRecordset("tbl_A")
rs.MoveFirst
    Do Until rs.EOF
        If rs.Fields(0).Value = strA And rs.Fields(1).Value = strB Then
            dblA = rs.Fields(2).Value
        End If
        rs.MoveNext
    Loop
End Sub

现在，如何清除可选参数的值?在进行某些计算时，我将需要它.像这样:

Now, how can I clear the value of an optional parameter? I will need this for some of the calculations. Something like:

Set strA = Nothing

推荐答案

更改子项并添加ByVal

Public Sub CalculateMe(Optional ByVal strA As String, Optional ByVal strB As String)

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