设计模式：lession3

一、工厂模式

概述：

• 工厂模式对new对象进行单独封装
• 遇到new时，就应该考虑工厂模式

// 创造原型
class Protuct{
    constructor(name){
        this.name = name;
    }
    init(){
        console.log('init')
    }
    showA(){
        console.log('showA')
    }
    showB(){
        console.log('showB')
    }
}
//创建工厂
class Creator{
    create(name){
        return new Protuct(name)
    }
}

//运用程序
let creator = new Creator();
let p = creator.create('p1');

p.init();
p.showA();
p.showB();

二、单例模式：一个类只能有一个实例

• 登陆框
• 购物车

//java语言中的演示
public class SingleObject{
//私有化变量，外部不能new,只能内部new!!!
    private SingleObject(){

    }
    // 惟一被new出来的对象
    private SingleObject instance = null;
    // 获取对象的惟一接口
    public SingleObject getInstance(){
        if(instance == null){
            instance = new SingleObject();
        }
        return instance
    }
    public void login(username,password){
        System.out.println('login...')
    }
}

• javascript演示

class SingleObject{
    login(){
        console.log('login...')
    }
}

SingleObject.getInstance = (function(){
    let instance 
    return function(){
        if(!instance){
            instance = new SingleObject()
        }
        return instance
    }
})()

let obj1 = SingleObject.getInstance();
obj1.login();
let obj2 = SingleObject.getInstance();
obj2.login();

console.log('obj1===obj2',obj1===obj2)