我有一个函数可以查找下周一的日期。当没有传递可选日期参数时,它将变为默认值零。我想我已经添加了注释来解释问题
Function NextMondayFromADateOrToday(Optional StartDate As Date) As Date
' objective: if date param not supplied should set StartDate to today
' ??? Problem: with no arg provided StartDate is zero = date value of 1/1/1900
' ??? how to add default to optional paramater of date type?
' ??? or, how to check if an arg was provided if the parameter is date type?
If Not (IsDate(StartDate)) Then StartDate = Date
Select Case Weekday(StartDate)
Case 1: NextMondayFromADateOrToday = StartDate + 1
Case 2: NextMondayFromADateOrToday = StartDate + 0
Case 3: NextMondayFromADateOrToday = StartDate + 6
Case 4: NextMondayFromADateOrToday = StartDate + 5
Case 5: NextMondayFromADateOrToday = StartDate + 4
Case 6: NextMondayFromADateOrToday = StartDate + 3
Case 7: NextMondayFromADateOrToday = StartDate + 2
End Select
End Function
VBA 变量通常有一个默认值,并且任何可选参数都会自动设置为其默认值,因此这种行为是预期的。既然您已经知道如果不传递可选参数将默认为 0 (1/1/1900),为什么不只测试该值而不是测试是否传递了日期呢?
另一方面,如果您认为某人可能需要传入 1/1/1900,那么您应该将可选参数设置为Variant
类型。可选地传入时,变量不会被初始化,因此它不会有默认值(与日期不同)。
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