装饰器模式

[louzhedong]

装饰器模式

动态地给一个对象添加一些额外的职责。

优点：

装饰类和被装饰类可以独立开发，不会互相耦合。

缺点：

多层装饰会比较复杂

实现

Java

/**
 * 抽象构件
 **/
public abstract class Component {
    public abstract void operate();
}

/**
 * 具体构件
 **/
public class ConcreteComponent extends Component {
    @Override
    public void operate() {

    }
}

/**
 * 抽象修饰器
 **/
public abstract class Decorator extends Component{
    private Component component = null;

    public Decorator(Component _component) {
        this.component = _component;
    }

    @Override
    public void operate() {
        this.component.operate();
    }
}

/**
 * 具体修饰器
 **/
public class ConcreteDecorator extends Decorator{
    public ConcreteDecorator(Component _component) {
        super(_component);
    }

    private void method() {}

    @Override
    public void operate() {
        this.method();
        super.operate();
    }
}

public class Client {
    public static void main(String[] args) {
        Component component = new ConcreteComponent();

        component = new ConcreteDecorator(component);

        component.operate();
    }
}

JavaScript

Function.prototype.before = function (beforefn) {
  const _this = this;
  return function () {
    beforefn.apply(this, arguments);
    return _this.apply(this, arguments);
  }
}

Function.prototype.after = function (afterfn) {
  const _this = this;
  return function () {
    const ret = _this.apply(this, arguments);
    afterfn.apply(this, arguments);
    return ret;
  }
}

// 例子
Function.prototype.before = function (beforefn) {
  const _this = this;
  return function () {
    if (beforefn.apply(this, arguments) === false) {
      return;
    }
    return _this.apply(this, arguments);
  }
}

const validata = function () {
  if (username.value === '') {
    return false;
  }
  if (password.value === '') {
    return false;
  }
}

let formSubmit = function () {
  const param = {
    username: username.value,
    password: password.value
  }
  ajax('http://aa.com', param);
}

formSubmit = formSubmit.before(validata);

submitBtn.onclick = function () {
  formSubmit();
}