如何从父方法为子类创建实例？
例如：
class Vehicle {
public getNewInstance(): ICar {
// What should be here?
return new XXXXXXXX;
}
}
class Car extends Vehicle {
public getWheels(): Number {
return 4;
}
}
现在,我需要这样做以获得一个新的Car实例：
Car.getNewInstance();
车辆有许多扩展类,我防止在每个孩子中重复代码.此外,儿童班也有更多的孩子.
解决方法
您的代码不会这样做,因为您需要静态方法而不是实例方法.
你可以这样做：
class Vehicle {
public static getNewInstance(): Vehicle {
return new this();
}
public getWheels(): Number {
throw new Error("unknown number of wheels for abstract Vehicle");
}
}
class Car extends Vehicle {
public getWheels(): Number {
return 4;
}
}
因为Vehicle现在有一个静态getNewInstance方法,所以所有扩展类也都有.
所以：
let v = Vehicle.getNewInstance();
console.log(v); // Vehicle {}
console.log(v.getWheels()); // Uncaught Error: unknown number of wheels for abstract Vehicle
let c = Car.getNewInstance();
console.log(c); // Car {}
console.log(c.getWheels()); // 4
编辑
如果我误解了你并且你确实想在现有实例上调用getNewInstance,那么你可以这样做：
abstract class Vehicle {
public abstract getNewInstance(): Vehicle;
}
class Car extends Vehicle {
public getNewInstance(): Vehicle {
return new Car();
}
public getWheels(): Number {
return 4;
}
}
或这个：
class Vehicle {
private ctor: { new (): Vehicle };
constructor(ctor: { new (): Vehicle }) {
this.ctor = ctor;
}
public getNewInstance(): Vehicle {
return new this.ctor();
}
}
class Car extends Vehicle {
constructor() {
super(Car);
}
public getWheels(): Number {
return 4;
}
}