Question

我正在尝试使用自定义类来使用合成覆盖其超类中的方法。下面是我尝试的代码，在类“Bar”中什么对象调用方法doSomethingElse（）？这不是我的代码，而是与问题相关联 - Using composition over inheritance when overriding

所有实例化都在子类中进行。

class Child extents Parent(){

public Child(){
   super();
   addButtons():
}
 addButtons(){
   <custom code here>
}

}


class Parent(){
 addButtons(){
   add(button1);
}
}

interface SomeMethods {
  void doSomething();
  void doSomethingElse();
}

class Foo implements SomeMethod {
  public void doSomething() { // implementation }
  public void doSomethingElse() { // implementation }
}

class Bar implements SomeMethod {
   private final Foo foo = new Foo();

   public void doSomething() { foo.doSomething(); }
   public void doSomethingElse() { // do something else! }
}

Answer 1

你很接近，只需使用Bar类

class Bar extends Foo {
   // note Bar is still of type SomeMethods because it extends a class of that type.
   public void doSomething() {
      super.doSomething();
      //add more code here if you want to do some more stuff, note you don't need to define this function if you don't need to do anything else.
   }
   public void doSomethingElse() {
      //don't call super, and do whatever you like
   }
}

Answer 2

如果您的原始点是覆盖doSomethingElse，那么在使用Composition时，在Bar中您将所有其他方法（在本例中为doSomething）委托给Foo，并在Bar.doSomethingElse（）中添加重写行为

这可能是这样的：

public void doSomethingElse() {
    .... // custom stuff
    foo.doSomethingElse(); // this is the equivalent of an inheritance super call, so it's optional
    .... // other custom stuff
}

另外（与原始问题无关，但我不禁提及它）生成更好的代码，你应该注入Foo依赖，而不是将它耦合到Bar。

class Bar implements SomeMethod {
   private final SomeMethod foo;

   public Bar(SomeMethod foo) {
     this.foo = foo;  
   }

   public void doSomething() { foo.doSomething(); }
   public void doSomethingElse() { // do something else! }
}

使用构图

2 个答案: