打字稿中的类构造函数类型？

Question

我如何声明一个class类型,以便我确保该对象是一个通用类的构造函数？

在下面的例子中,我想知道我应该给哪种类型,AnimalClass以便它可以是Penguin或Lion:

class Animal {
    constructor() {
        console.log("Animal");
    }
}

class Penguin extends Animal {
    constructor() {
        super();
        console.log("Penguin");
    }
}

class Lion extends Animal {
    constructor() {
        super();
        console.log("Lion");
    }
}

class Zoo {
    AnimalClass: class // AnimalClass could be 'Lion' or 'Penguin'

    constructor(AnimalClass: class) {
        this.AnimalClass = AnimalClass
        let Hector = new AnimalClass();
    }
}

当然,这种class类型不起作用,无论如何它都太普遍了.

Answer 1

来自typescript接口的解决方案参考:

interface ClockConstructor {
    new (hour: number, minute: number): ClockInterface;
}
interface ClockInterface {
    tick();
}

function createClock(ctor: ClockConstructor, hour: number, minute: number): ClockInterface {
    return new ctor(hour, minute);
}

class DigitalClock implements ClockInterface {
    constructor(h: number, m: number) { }
    tick() {
        console.log("beep beep");
    }
}
class AnalogClock implements ClockInterface {
    constructor(h: number, m: number) { }
    tick() {
        console.log("tick tock");
    }
}

let digital = createClock(DigitalClock, 12, 17);
let analog = createClock(AnalogClock, 7, 32);

所以前面的例子变成了:

interface AnimalConstructor {
    new (): Animal;
}

class Animal {
    constructor() {
        console.log("Animal");
    }
}

class Penguin extends Animal {
    constructor() {
        super();
        console.log("Penguin");
    }
}

class Lion extends Animal {
    constructor() {
        super();
        console.log("Lion");
    }
}

class Zoo {
    AnimalClass: AnimalConstructor // AnimalClass can be 'Lion' or 'Penguin'

    constructor(AnimalClass: AnimalConstructor) {
        this.AnimalClass = AnimalClass
        let Hector = new AnimalClass();
    }
}

Answer 2

像那样:

class Zoo {
    AnimalClass: typeof Animal;

    constructor(AnimalClass: typeof Animal ) {
        this.AnimalClass = AnimalClass
        let Hector = new AnimalClass();
    }
}

要不就:

class Zoo {
    constructor(public AnimalClass: typeof Animal ) {
        let Hector = new AnimalClass();
    }
}

typeof Class是类构造函数的类型.它比自定义构造函数类型声明更可取,因为它正确处理静态类成员.

Answer 3

如何声明类类型，以确保该对象是通用类的构造函数？

构造函数类型可以定义为：

 type AConstructorTypeOf<T> = new (...args:any[]) => T;

 class A { ... }

 function factory(Ctor: AConstructorTypeOf<A>){
   return new Ctor();
 }

const aInstance = factory(A);

Answer 4

我不确定最初问这个问题时在TypeScript中是否可行，但是我的首选解决方案是使用泛型：

class Zoo<T extends Animal> {
    constructor(public readonly AnimalClass: new () => T) {
    }
}

这样就可以变量penguin并lion推断具体类型Penguin，Lion甚至可以推断出TypeScript智能感知。

const penguinZoo = new Zoo(Penguin);
const penguin = new penguinZoo.AnimalClass(); // `penguin` is of `Penguin` type.

const lionZoo = new Zoo(Lion);
const lion = new lionZoo.AnimalClass(); // `lion` is `Lion` type.