装饰器模式

Question

有人可以帮我在javascript中实现Decorator设计模式吗？我有一个TankBase实体：

TankBase = function (x, y, width, height, direction, imageOptions) {
    TankBase.base.call(this, x, y, width, height, imageOptions);
    this.speed = 250;
    this.direction = direction;
    this.render = function (drawEngine) {
        drawEngine.render();
    };
    ...
}

我想使用Decorator模式添加新功能。例如，我想修改render（）函数并在tank下绘制一个健康指示器：

var TankHealthDecorator = function (tank) {
    var _tank = tank;
    this.render = function (drawEngine) {
        // draw a health indicator
        ...
        _tank.render(drawEngine);
    };
}

用法：

var tank = new TankHealthDecorator(new HeavyTank());

HeavyTank继承TankBase。

我应该如何修改TankHealthDecorator（）以像坦克实例的包装一样使用它？

修改

保罗，谢谢你的精彩文章：

我从这里开始：addyosmani.com/blog/decorator-pattern好写起来。 - 保罗

Answer 1

从功能上来说，我认为你拥有的非常接近。我将存储原始渲染功能，分配一个新功能，然后从装饰功能中简单地应用它。我也没有看到需要将装饰器创建为对象，但这可能更像是一种偏好。

var DrawEngine = { render: function() {
    console.log('render');
} };

var TankBase = function (x, y, width, height, direction, imageOptions) {
    this.speed = 250;
    this.direction = direction;
    this.render = function (drawEngine) {
        drawEngine.render();
    };
};

var HeavyTank = function() {
    TankBase.apply(this, arguments);
    this.render = function() {
        console.log('heavyTank Render');
    }
}

function DecorateTankWithHealthIndicator (tank) {
    var oRender = tank.render;
    tank.render = function (drawEngine) {
        console.log('draw a health indicator');
        oRender.apply(tank, arguments);
    };
};

var btank = new TankBase();
var htank = new HeavyTank();
btank.render(DrawEngine);
htank.render(DrawEngine);
DecorateTankWithHealthIndicator(btank);
DecorateTankWithHealthIndicator(htank);
btank.render(DrawEngine);
htank.render(DrawEngine);

Answer 2

在以下方法中，tankBase对象被传递给tankHealth函数。 tankBase对象在tankHealth函数中被修改，将tankBase对象保存在var that中。修改后的that作为修改后的tankBase对象返回。

var TankBase = function () {
        this.render = function () {
            console.log('tankBase')
        };
    }

var TankHealthDecorator = function (tank) {
    var that = tank;

    that.render = function() {
        console.log('tankHealth')
    };

    return that;
}

window.onload = function(){
    var tankBase = new TankBase();
    var testHealth = new TankHealthDecorator(new TankBase());

    tankBase.render();     // tank base
    testHealth.render();   // tank health
};

Answer 3

装饰器模式

以下是装饰器模式的粗略实现 - 又名： Wrapper ：

背景

装饰器模式通常用于通过将请求转发到其接受的组件和|或解耦，动态地向对象添加其他职责 深层继承层次结构在 Type 中 Compositive （不要与复合模式混淆 - 这是< em> Hierarchy中的em> Compositive - 使用 Component-Leaf 结构，允许跨均匀分形拓扑的同义请求[同等对待父母和孩子]

function AbstractComponent(){
    this.draw = function(){
        console.log('@AbstractComponent | #draw');
    };
}

function AbstractDecorator(){
    AbstractComponent.call(this);  // Inherit AbstractComponent Interface
    this.notify = function(){
        console.log('@AbstractDecorator | #notify');
    };
}

function ConcreteComponent(options){
    AbstractComponent.call(this);  // Inherit AbstractComponent Interface
    this.fill = function(){
        console.log('@ConcreteComponent | #fill');
    };
}

function ConcreteDecorator(Component){
    AbstractDecorator.call(this);  // Inherit AbstractDecorator Interface
    function PrivateResponsibility(){
        console.log('@ConcreteDecorator | #PrivateResponsibility');
    }
    this.additionalResponsibility = function(){
        console.log('@ConcreteDecorator | #additionalResponsibility');
    };
    this.draw = function(){
        console.log('@ConcreteDecorator | #draw-Component.draw');
        // ... additional logic
        PrivateResponsibility();
        Component.draw();
    };
    this.fill = function(){
        console.log('@ConcreteDecorator | #fill-Component.fill');
        Component.fill();
    };
}

var concreteComponent = new ConcreteComponent();
concreteComponent = new ConcreteDecorator(concreteComponent);  // use same variable name as to allow client code to remain the same

//CLIENT CODE
concreteComponent.draw();
concreteComponent.fill();
concreteComponent.notify();
concreteComponent.additionalResponsibility();

Answer 4

以下是我对功能（对象）装饰的理解

 function api_decorator(some_data){
     return function decorator(func){
        return function new_function(args){
         /* do somethinfg with data before and after func */
         console.log("I'm code before with data: "+some_data);
         func(args);
         console.log("I'm code after");
    }
  }
}

function somefunc(data){
    console.log("Hi, I'm func "+data);
}

somefunc("without decoration")
/* injecting somefunc in decorator api */
somefunc=api_decorator("data needed for api")(somefunc)
/* calling decorated with api somefunc */
somefunc("with decoration")

如何在javascript中实现Decorator设计模式？

4 个答案:

装饰器模式

背景