定义
代理模式是为一个对象提供一个代用品,或占位符,以便控制对它的访问。
实现
思路:把客户端真正调用的类和方法隐藏,只暴露代理类给客户端。
简单点的例子:
// 食品服务接口
interface FoodService {
makeChicken (salt: string): void;
makeNoodle (salt: string): void
}
// 食物接口
class Food {
// 种类
public type: string
// 重量
public salt: string
public constructor (type: string, salt: string) {
this.type = type
this.salt = salt
this.cook()
}
// cook
public cook (): void {
console.log(`种类:${this.type},重量:${this.salt}`)
}
}
// 真实的食品服务
class FoodServiceReal implements FoodService {
public chicken: Food
public Noodle: Food
public makeChicken (salt: string): any {
this.chicken = new Food('chicken', salt)
}
public makeNoodle (salt: string): any {
this.Noodle = new Food('noodle', salt)
}
}
// 代理食品服务
class FoodServiceProxy implements FoodService {
// 真实的实现类
private foodServiceReal: FoodServiceReal
private prepareFood () {
if (!this.foodServiceReal) {
this.foodServiceReal = new FoodServiceReal()
}
}
public makeChicken () {
console.log('马上开始做鸡肉')
console.log('==========')
this.prepareFood()
this.foodServiceReal.makeChicken('500g')
console.log('==========')
console.log('鸡肉做好了')
}
public makeNoodle () {
console.log('马上开始做面条')
console.log('==========')
this.prepareFood()
this.foodServiceReal.makeNoodle('100g')
console.log('==========')
console.log('面条做好了')
}
}
const food = new FoodServiceProxy()
food.makeChicken()
console.log('========')
food.makeNoodle()
缓存代理比较常见,可以为一些开销比较大的运算结果提供缓存,在下次运算时,如果传递进来的参数跟以前一致,则可以直接返回前面存储的运算结果。
// 加法
function add (arg: Array<number>): number {
console.log('进行一次加法计算')
return arg.reduce((prev: number, cur: number): number => prev + cur, 0)
}
// 乘法
function mul (arg: Array<number>): number {
console.log('进行一次乘法计算')
return arg.reduce((prev: number, cur: number): number => prev * cur, 1)
}
// 代理
class CalculateProxy {
private cache: Object = {}
private fn: Function
public constructor (fn: Function) {
this.fn = fn
}
public calculate (...arg: Array<number>): void {
const str: string = arg.join(',')
if (str in this.cache) {
return this.cache[str]
} else {
return this.cache[str] = this.fn(arg)
}
}
}
const addCalculateProxy = new CalculateProxy(add)
console.log(addCalculateProxy.calculate(1, 2, 3, 4))
console.log(addCalculateProxy.calculate(1, 2, 3, 4))
console.log('=========')
const mulCalculateProxy = new CalculateProxy(mul)
console.log(mulCalculateProxy.calculate(1, 2, 3, 4))
console.log(mulCalculateProxy.calculate(1, 2, 3, 4))
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