VB6成员变量继承

Question

我在继承 (public) 变量时遇到问题，比方说

Public Var As ClassThatIsIndependent

上面的声明本身不会产生任何问题，但是，如果我继承了包含它的 class

Implements BaseClass

我收到错误 "object module needs to implement variable for interface"。我已经尝试了这些选项（都在 ChildClass 中）

Public Var As ClassThatIsIndependent

和

Public BaseClass_Var As ClassThatIsIndependent

但是其中 none 解决了问题。还有其他选择吗？我对可能的 Set/Get 解决方案持开放态度，但是，我更愿意将 Var 维护为 public 变量。

Answer 1

根据 Visual Basic 6.0 程序员指南，多态性，Implementing Properties 部分：

Suppose we give the Animal class an Age property, by adding a Public variable to the Declarations section:
Option Explicit
Public Age As Double
The Procedure drop downs in the code modules for the Tyrannosaur and Flea classes now contain property procedures for implementing the Age property,

…

Using a public variable to implement a property is strictly a convenience for the programmer. Behind the scenes, Visual Basic implements the property as a pair of property procedures.

You must implement both procedures. The property procedures are easily implemented by storing the value in a private data member, as shown here:
Private mdblAge As Double

Private Property Get Animal_Age() As Double
   Animal_Age = mdblAge
End Property

Private Property Let Animal_Age(ByVal RHS As Double)
   mdblAge = RHS
End Property
The private data member is an implementation detail, so you have to add it yourself.

也就是说，无论您使用 Public 变量还是使用属性 Get/Let 定义它们，"public interface" 都完全相同。要在接口中实现属性，您不能使用 Public 变量方法，需要使用属性 Get/Let 语法并在其中处理数据存储你自己的私有变量。

VB6成员变量继承

VB6 Member variable inheritance

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variables

inheritance

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