航空发动机行业现状:能否判断动态数组有没有被分配过

来源:百度文库 编辑:九乡新闻网 时间:2024/04/28 13:06:42
动态数组在VB语言中常能起到出奇制胜的作用。但数组有没有被重新定义或释放,用“is empty”,“is null”,“=""”等方法都不起作用。所以判断时一般采用侦别错误消息(ON ERROR )的方法。下面给出一个非错误侦别的代码,判断动态字符串数组的分配情况:

 

 

Private Sub Command1_Click()
Dim a() As String, i As Long


MsgBox hasredim(a), 64, "Has a() been redimed?"   ´未初始化


ReDim a(20)

For i = 1 To 20
a(i) = chr(i+64)

Next

MsgBox hasredim(a), 64, "Has a() been redimed?"     ´初始化后


Erase a    ´释放空间后
MsgBox hasredim(a), 64, "Has a() been redimed?"   


End Sub

 


Function hasredim(ByRef x() As String) As Boolean  ´定义布尔函数
Dim temp As String
temp = Join(x, ",")
hasredim = LenB(temp) > 0 ´空数组长度为零
End Function