用泛型T扩展类 [英] extending a class with a generic T

问题描述

在TypeScript中，有没有一种方法可以用通用类型扩展类?请参考我的假设场景"示例，在该示例中，我希望我的班级拥有一个名为繁殖"(或其他名称)的属性:

In TypeScript is there a way to extend a class with a generic type? Refer to my "hypothetical scenario" example where I want my class to have property called "breed" (or whatever):

interface dog {
  breed: string;
}

export class animal<T> extends T {
  legs: number;
}

export class main {
  private mydog: animal = new animal<dog>();

  constructor() {
    this.mydog.legs = 4;
    this.mydog.breed = "husky"; //<-- not conventionally possible, but basically want to acheive this
  }
}

推荐答案

您不能这样做，因为类是在编译时定义的，并且在 animal 类被编译时是 T 未知.

You can't because classes are defined at compile time, and when the animal class is compiled T is not known.

不过，您可以在动物内定义类型为 T 的属性.

You can however define a property of type T inside animal.

interface dog {

  breed: string;

}

export class animal < T > {
  actual: T;
  legs: number;
}

export class main {

  private mydog: animal < dog > = new animal < dog > ();

  constructor() {

    this.mydog.legs = 4;
    this.mydog.actual.breed = "husky"; // this will fail because actual is undefined (you must set it too)
  }

}

我想这取决于您为什么需要动物类为通用类，但是您也可以只用狗扩展动物.

I guess it depends on why you need the animal class to be generic, but you can also just have dog extend animal.

export class animal {
  legs: number;
}

class dog extends animal {
  breed: string;
}

export class main {

  private mydog: dog = new dog();

  constructor() {

    this.mydog.legs = 4;
    this.mydog.breed = "husky";
  }

}

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