inheritance - ES6 et al. is it possible to define a catch-all method?

Question

Composition is a useful alternative to inheritance when one wants to cascade method calls from child to parent, see child extended class method calls its super version but that still only sees child data

However, for the child to present an interface that is compatible with parent type, one must implement a potentially large number of stub methods that all have the same form, namely they just relay the call to the former parent (which is now a component).

My question here, is it possible to write a catch-all method? A catch-all method would be called when none of the other methods are called. The catch-all would then just relay calls to the parent component. Thus the stub would only have to be written once. Variations could be used to sort multiple inheritance, etc.

Something like this:

  class A {
      constructor(){
        this.x = "super x!";
      }
      f(){
        console.log("I am a super f()!");
      }
      logx(){
        this.f();
        console.log(this.x);
      }
    }

    class B {
      constructor(){
        this.a = new A();
        this.x = "derived x.";
      }
      f(){
        console.log("I am a derived f()");
      }
      logx(){
        this.a.logx();
      }
    }

    let b = new B;
    b.logx();

  I am a super f()!
    super x!

Hypothetically would instead be something like this:

 class A {
      constructor(){
        this.x = "super x!";
      }
      f(){
        console.log("I am a super f()!");
      }
      logx(){
        this.f();
        console.log(this.x);
      }
    }

    class B {
      constructor(){
        this.a = new A();
        this.x = "derived x.";
      }
      f(){
        console.log("I am a derived f()");
      }
      catch_all(method_name, ...args){
        this.a.method_name(...args);
      }
    }

    let b = new B;
    b.logx();

  I am a super f()!
    super x!

Answer 1

这建立在 isepa 的建议之上，即使用 Fred Truter 的函数来列出方法。这是一个很好的概念，但它并不能完全让我们到达那里。它需要进行测试，以免破坏现有方法。同样只是复制方法是有问题的，因为父 this.variables 将不存在或将在子中别名 - 请注意这是组合，因此它们不打算被继承。这不是复制，而是将其变成调用。

    //Fred Truter's function:
    Object.methods = function (klass) {
      const properties = Object.getOwnPropertyNames(klass.prototype)
      properties.push(...Object.getOwnPropertySymbols(klass.prototype))
      return properties.filter(name => {
        const descriptor = Object.getOwnPropertyDescriptor(klass.prototype, name)
        if (!descriptor) return false
        return 'function' == typeof descriptor.value && name != 'constructor'
      })
    }

   Object.compose = function (obj0, obj1, ...constructor_args) {
    obj0[obj1.name] = new obj1(...constructor_args);
    Object.methods(obj1).forEach(
      method => {
        if(!obj0[method]) obj0[method] = (...args) => obj0[obj1.name][method](...args);
      }
    );
  }


    // shows using the composition operator:
    class A {
      constructor(){
        this.x = "super x!";
      }
      f(){
        console.log("I am a super f()!");
        console.log(this.x);
      }
      logx(){
        console.log(this.x);
        this.f();
      }
    }

    class B {
      constructor(){
        Object.compose(this, A);
        this.x = "derived x.";
      }
      // f(){ console.log("I am a derived f()"); }
      logx(){
        console.log(this.x);
        this.f();
      }
    }

    let b = new B;
    b.logx();
    b.f();

正如预期的那样，输出：

derived x.
I am a super f()!
super x!
I am a super f()!
super x!

然后从 f 的子版本中删除注释后，我们得到了预期的结果：

derived x.
I am a derived f()

Answer 2

使用 Fred Truter 的函数从类中提取方法遍历 ES6 类的方法和属性：

Object.methods = function (klass) {
    const properties = Object.getOwnPropertyNames(klass.prototype)
    properties.push(...Object.getOwnPropertySymbols(klass.prototype))
    return properties.filter(name => {
        const descriptor = Object.getOwnPropertyDescriptor(klass.prototype, name)
        if (!descriptor) return false
        return 'function' == typeof descriptor.value && name != 'constructor'
    })
}

class A {
    constructor() {
        this.x = "super x!";
    }
    f() {
        console.log("I am a super f()!");
    }
    logx() {
        console.log(this.x + "log");
    }
}

class B {
    constructor() {
        this.a = new A();
        this.x = "derived x. ";
        Object.methods(A).forEach(method => this[method] = this.a[method]);
    }
    logx() {
        console.log(this.x + "log")
    }
}

let b = new B;
b.f(); //"I am a super f()!"
b.logx(); //"derived x. log"