Typescript type of concrete subclasses of an abstract class

Question

I'm trying to resolve this specific case in Typescript:

Typescript Playground link

abstract class foo {
    abstract bar();
}

class Foo1 extends foo {
    bar() {
        alert(1);
    }

    y: number = 3;
}

class Foo2 extends foo {
    bar() {
        alert(2);
    }
}

let myFooClasses: Array<typeof foo> = [];
myFooClasses.push(Foo1);
myFooClasses.push(Foo2);

myFooClasses.forEach((item) => {
    let a = new item();
    a.bar();
})

Specifically, the problem is that myFooClasses could technically contain foo which is abstract and Typescript warns about this. But I really want to constrain the type of myFooClasses to concrete classes inheriting from foo. Is there any way of specifying this in Typescript?

Answer 1

Your array type should be:

let myFooClasses: Array<{ new (): foo }> = [];

and then this:

myFooClasses.push(foo);

produces this error:

Argument of type 'typeof foo' is not assignable to parameter of type '{ new (): foo }'. Can not assign an abstract constructor type to a non-abstract constructor type.

You can also do:

type FooConstructor = { new (): foo };
let myFooClasses: FooConstructor[] = [];