使用 Vbex2005 将继承重构为组合
我在 vb.net 编程经验中很早就编写了一个类，它继承自它真正应该组成的另一个类。基类是一个相对通用的基于嵌套字典的集合；我们将后代类称为“Car”。
现在有很多代码可以执行诸如 'MyCar!Color.st = "Red"' 之类的操作（我使用通用集合而不是实际属性来方便与 VB6 编写的代码进行数据交换，也方便对汽车进行比较；给定三辆车 X、Y、Z，我可以检测 X 和 Y 之间的任何变化并将这些变化应用到 Z）。
有没有什么好的方法来重构代码以使用组合而不是继承？ “Car”对象应该包装哪些属性/方法，以及应该通过数据对象属性访问哪些属性/方法？是否应该在汽车和集合对象之间定义扩大转换？进行此类重构时是否存在任何问题？
I have a class that I wrote fairly early on in my vb.net programming experience which inherited from another class it really should have composed. The base class is a relatively generic nested dictionary-based collection; let's call the descendant class a "Car".
Right now there's a lot of code that does things like 'MyCar!Color.st = "Red"' (I use the generic collection rather than real properties to facilitate data interchange with code written in VB6, and also to facilitate comparisons of cars; given three cars X, Y, Z, I can e.g. detect any changes between X and Y and apply those changes to Z).
Is there any nice way to refactor the code to use composition rather than inheritance? Which properties/methods should the "Car" object wrap, and which ones should be accessed through a data-object property? Should a widening conversion be defined between a car and the collection object? Are there any gotchas when doing such refactoring?
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你可以首先说 Car 有一个函数（或方法；不确定 vb.net 术语）来获取其集合 - 该函数最初会返回
this（或self，或者任何 vb 的称呼）。现在，将 Car 类内部和外部对 Car-as-Collection 的所有直接引用替换为
Car.getCollection()。最后，进行更改：创建一个成员变量，对其进行初始化，从
getCollection()返回它，并停止从 Collection 继承。如果您在第 2 步中错过了任何引用，此时它们将显示为编译错误。修复它们，您的重构就完成了。You could start by saying Car has a function (or method; not sure of the vb.net terminology) to get its collection - and that function would initially return
this(orself, or whatever vb calls it).Now replace all direct references to Car-as-Collection with
Car.getCollection(), both within the Car class and outside.Finally, make the change: create a member variable, initialize it, return it from
getCollection(), and stop inheriting from Collection. If you missed any references in step 2, they'll show up as compile errors at this point. Fix them and your refactoring is complete.