vba VBA如何从函数返回null
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VBA How to return null from a function
提问by Tristian
I have this function
我有这个功能
Public Function parseEmployee(ByVal employeeId As Integer, _
ByVal ws As Worksheet) As employee
Dim emp As New employee
Dim empRow As Range
If sheetContainsEmployee(employeeId, ws) Then
Set empRow = ws.Rows(ws.Columns(ID_COLUMN).Find(employeeId).Row)
emp.id = employeeId
emp.Name = empRow.Cells(1, NAME_COLUMN).Value
Else
emp = Null ' Heres what I'd like to do
End If
parseEmployee = emp
End Function
And I'd like to return null in case that the employee is not found in the sheet, is that possible? I get an object or variable nblock not set. error
如果在工作表中找不到该员工，我想返回 null，这可能吗？我得到一个未设置的对象或变量 nblock。错误
回答by Mitch Wheat
Only a Variantcan be Null, instead use Nothing:
只有 aVariant可以是Null，而是使用Nothing：
Public Function parseEmployee(ByVal employeeId As Integer, _
ByVal ws As Worksheet) As employee
Dim emp As New employee
Dim empRow As Range
If sheetContainsEmployee(employeeId, ws) Then
Set empRow = ws.Rows(ws.Columns(ID_COLUMN).Find(employeeId).Row)
emp.id = employeeId
emp.Name = empRow.Cells(1, NAME_COLUMN).Value
Else
Set emp = Nothing
End If
Set parseEmployee = emp
End Function
The way you would test:
你会测试的方式：
Dim emp As employee
Set emp = parseEmployee( ... )
If emp Is Nothing Then
Debug.Print "No employee returned."
End If
回答by AKirby50
I have found that returning Nothing from a function causes an exception.
我发现从函数返回 Nothing 会导致异常。
What I did instead was to write a sub that takes a ByRef parameter that is your return value.
我所做的是编写一个子程序，它接受一个 ByRef 参数作为您的返回值。
Instead of this:
取而代之的是：
Public Function test() as SomeClass
set test = Nothing
End Function
I wrote this:
我写了这个：
Public Sub test(ByRef result as SomeClass)
result = Nothing
End Sub
回答by Heidi
just use """", or "", which one will work, you could try, as:
只需使用“”“”或“”，哪个有效，您可以尝试，如：
Else Set emp = """"
否则设置 emp = """"
note that there is no space between
请注意，之间没有空格
