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首页 - 经验之谈 - An OO way to pass Visual Basic variable values to a form
发表评论(0)作者:不详, 平台:VB6.0+Win98, 阅读:13771, 日期:2000-10-15
Object oriented programming guidelines stipulate that objects--including forms--should maintain their own internal values. With this in mind, you注释:ll need a way to pass values to loaded forms without using universally global variables. Fortunately, Visual Basic provides just such a way with its property Let() and Get() procedures.

For example, suppose you have a button Click() event on Form1 that loads Form2. Form2 displays a value collected in Form1. In the past, you may have created a public variable with an application scope, and then read this variable in Form2 to obtain the proper value. Using this technique, however, soon results in hard-to-manage, spaghetti code.

As a more elegant alternative, you can add a property to Form2 that Form1 can then set.

For instance, in Form2 you would add the following property procedures along with the variable declaration:

Private myVar as Variant

Public Property Get PassVar() As Variant
PassVar = myVar
End Property

Public Property Let PassVar(ByVal vNewValue As Variant)
If IsNumeric(vNewValue) Then myVar = vNewValue
End Property

For these procedures, you can change the property type, but it must match in both the Get and Let procedures. Also notice that we included some validation code to ensure that the passed value is a number.

Now, to read or assign a value to this property, use the following code on Form1

Private Sub Command1_Click()
With Form2
    .PassVar = 25
    Debug.Print .PassVar
End With
End Sub