Typescript - returning the constructor of a child class from an abstract method

Question

I have abstract class Child and abstract class Parent as follows:

abstract class Child {

}

abstract class Parent {
  abstract getChild(): typeof Child; // <-- want a class that extends Child
}

The idea is that both Parent and Child are extended by actual implementation classes, where each implementation Parent knows what its Child class is:

class ActualChild extends Child {

}

class ActualParent extends Parent {
  getChild() {
    return ActualChild;
  }
}

As far as TS is concerned, the returned object is of type Child, and thus cannot be instantiated.

I tried many different ways to explain that the function returns only a class that extends Child without success.

Is there any way to type that?

Answer 1

Declare an interface to describe the abstract class Child itself, and change the return type of getChild() to be that interface.

interface ChildConstructor {
  new(): Child;
}


abstract class Parent {
  abstract getChild(): ChildConstructor;
}

Then this will compile without TypeScript errors:

const parentInstance: Parent = new ActualParent();
const ChildClass = parentInstance.getChild();
const childInstance = new ChildClass();