Typescript基本概念2

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1. 声明合并

ts声明的重名的类或命名空间，会进行合并

类合并

interface Box {
    height: number;
    width: number;
}

interface Box {
    scale: number;
}

let box: Box = {height: 5, width: 6, scale: 10};

命名空间合并

namespace Animals {
    export class Zebra { }
}

namespace Animals {
    export interface Legged { numberOfLegs: number; }
    export class Dog { }
}

//等同于
namespace Animals {
    export interface Legged { numberOfLegs: number; }

    export class Zebra { }
    export class Dog { }
}

2. mixins

ts的mixins主要是用来实现类的多继承。可以用类来implements多个类，这样只会继承成员，方法不会。

在子类中将继承的属性和方法声明占位，用原型复制的方式，添加真正的方法。

// Disposable Mixin
class Disposable {
    isDisposed: boolean;
    dispose() {
        this.isDisposed = true;
    }

}

// Activatable Mixin
class Activatable {
    isActive: boolean;
    activate() {
        this.isActive = true;
    }
    deactivate() {
        this.isActive = false;
    }
}

class SmartObject implements Disposable, Activatable {
    constructor() {
        setInterval(() => console.log(this.isActive + " : " + this.isDisposed), 500);
    }

    interact() {
        this.activate();
    }

    // Disposable
    isDisposed: boolean = false;
    dispose: () => void;
    // Activatable
    isActive: boolean = false;
    activate: () => void;
    deactivate: () => void;
}
applyMixins(SmartObject, [Disposable, Activatable]);

let smartObj = new SmartObject();
setTimeout(() => smartObj.interact(), 1000);

////////////////////////////////////////
// In your runtime library somewhere
////////////////////////////////////////

function applyMixins(derivedCtor: any, baseCtors: any[]) {
    baseCtors.forEach(baseCtor => {
        Object.getOwnPropertyNames(baseCtor.prototype).forEach(name => {
            derivedCtor.prototype[name] = baseCtor.prototype[name];
        });
    });
}