打字稿：至少实现特定接口的类

Question

I have the following question. Let's say i have an Interface like this

interface Animal<T>{
   children: Array<T>
}

now i want to write a method which will later take in eg a bird (a class that implements Animal). At the time writing the method the definition for bird does not exist yet. It could also be it would be given an instance of Shark. But the minimal requirement will be that any object it receives will be an instance of a class that implements Animal.

function doSomething(AnAnimal){
   //Do something with animal
}

// Implementation with a class that implements Animal

class Bird<T> implements Animal{
   children: Array<T>;
   color: string;
   chirp(){console.log('peep')}

   constructor(Color:string){
      this.color = Color;
   }
}

let tweety = new Bird('yellow');

doSomething(Tweety)

I hope I could make clear what I'm trying to do and you have an idea how i could solve this in TypeScript.

Answer 1

You need to flow your type arguments throughout your example...

interface Animal<T>{
   children: Array<T>
}

function doSomething<T>(arg: Animal<T>){
   //Do something with animal
}

class Bird<T> implements Animal<T>{
   children: Array<T>;
   color: string;
   chirp(){console.log('peep')}

   constructor(Color:string){
      this.color = Color;
   }
}

let tweety = new Bird('yellow');

doSomething(tweety);

For example, Bird<T> must implement Animal<T> . The doSomething function must be generic in order to deal with an argument of type Animal<T> .

Non-Generic Version

You might find that you are tying yourself up unnecesarily in type arguments here - so you might want to try the non-generic version.

interface Animal {
    children: Array<Animal>;
}

function doSomething(arg: Animal) {
    //Do something with animal
}

class Bird implements Animal {
    children: Array<Bird>;
    biggestEnemy: Animal;
    color: string;
    chirp() { console.log('peep') }

    constructor(Color: string) {
        this.color = Color;
    }
}

let tweety = new Bird('yellow');

doSomething(tweety);