使用组合而不是继承的装饰图案 [英] Decorator Pattern Using Composition Instead of Inheritance

问题描述

我以前对装饰器模式的理解是，您使用 WindowDecorator 继承 Window ，然后在重写的方法中，在调用 Window 实现所述方法之前，请先进行一些额外的工作。类似于以下内容：

My previous understanding of the decorator pattern was that you inherit Window with WindowDecorator, then in the overridden methods, do some additional work before calling the Window's implementation of said methods. Similar to the following:

public class Window
{
    public virtual void Open()
    {
        // Open the window
    }
}

public class LockableWindow : Window // Decorator
{
    public virtual void Open()
    {
        // Unlock the window
        base.Open();
    }
}

然而，这实际上是硬编码装饰，那么这样被重构使用组合而不是继承？

However this essentially hardcodes the decoration, so how would this be refactored to use composition instead of inheritance?

推荐答案

对不起，我的C＃有点（好吧，非常）生锈，所以有可能是一些语法错误，但基本思想是正确的。

Sorry, my C# is a a bit (OK, very) rusty, so there may be a few syntax errors, but the basic idea is right.

public interface IWindow
{
    void Open();
}

public class Window : IWindow
{
    public virtual void Open()
    {
        // Open the window
    }
}

public class LockableWindow : IWindow
{
    private IWindow _wrappedWindow;

    public LockableWindow(IWindow wrappedWindow)
    {
        _wrappedWindow = wrappedWindow;
    }

    public virtual void Open()
    {
        // TODO Unlock window if necessary
        _wrappedWindow.open();
    }
}

要注意的关键是新的$ $ c> IWindow interface;这就是允许您继续使用多态性。

The key thing to notice is the new IWindow interface; that's what allows you to keep using polymorphism.

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