VBA提高篇_19 可选参数Optional_ IsMissing _MSgbox

1. 可选参数Optional

Optional 代表本参数是可选项 =False ; 代表参数若不指定,则默认为False

Function mySumProduct(r As Range, Optional useColumn As Boolean = False)
End Function

Function mySumProduct(r As Range, Optional useColumn As Boolean = False)Dim i&, j&, s&, k&s = 0If useColumn ThenFor j = 1 To r.Columns.Countk = 1For i = 1 To r.Rows.Countk = k * r.Cells(i, j)Next is = s + kNext iElseFor i = 1 To r.Rows.Countk = 1For j = 1 To r.Columns.Countk = k + r.Cells(i, j)Next js = s + kNext imySumProduct = sEnd Function

---

2.IsMissing判断参数是否提供,只能判断变体类型

3. 使用 := 可以按参数名传递参数 a:=1,c:=3

Sub callDemo()Dim xx = myFun(3)'x = myFun(3, 4)'x = myFun(3, 4, 5)'x = myFun(a:=3, c:=1)End SubFunction myFun(a, Optional b = 0, Optional c = 0)myFun = a + b - cEnd Function

4.Msgbox 常用参数

Prompt: 第一参数,字符串
Buttons: 第二参数, Msgbox风格代码(可用常量名称,可用风格代码)
Title:第三参数, 对话框标题栏

. Msgbox的返回值代码

5.VBA颜色常量表