VB6 按值传递和按引用传递

VB6中的参数传递方式有两种，分别是按值传递和按引用传递。按值传递是指将参数的值复制一份，然后将复制的值传递给函数或子程序进行处理；而按引用传递是指将参数的内存地址传递给函数或子程序，使其可以直接操作参数的值。

vb
Sub ChangeValue(ByVal num As Integer)
    num = 100
End Sub
Sub Main()
    Dim x As Integer
    x = 10
    ChangeValue(x)
    MsgBox x ' 输出结果为10，原始值不受影响
End Sub

vb
Sub ChangeValue(ByRef num As Integer)
    num = 100
End Sub
Sub Main()
    Dim x As Integer
    x = 10
    ChangeValue(x)
    MsgBox x ' 输出结果为100，原始值被修改
End Sub

vb
Sub ChangeValue(ByVal num As Integer)
    num = 100
End Sub
Sub ChangeValue2(ByRef num As Integer)
    num = 100
End Sub
Sub Main()
    Dim x As Integer
    x = 10
    
    ChangeValue(x)
    MsgBox x ' 输出结果为10，原始值不受影响
    
    ChangeValue2(x)
    MsgBox x ' 输出结果为100，原始值被修改
End Sub