Nrthugu

Let's say we have a file with this class in it:

class Foo<T> {

  bar: T;

  constructor(bar: T) {

    this.bar = bar;

  }

}



function getFooType() {

    return Foo;

}

In another file, the return value of getFooType() gets passed in:

function baz(fooType: ???) {

  let foo1 = new fooType<number>(1);

  let foo2 = new fooType<string>("2");

}

I cannot for the life of me figure out what should go into ???.

The natural choice would be Class<Foo<T>>, but that forces you close the T by doing baz<T>(...), whereas I want it to stay open; you'll get errors like "Cannot construct non-polymorphic Foo [1] with type arguments." where you do new fooFactory<...>()

So the other obvious choice is using Class<Foo>, but then you get the error "Cannot use Foo [1] without 1 type argument." on that parameter.

In fact, it looks like it's not possible to pass a class' type around if it has a generic type specifier. Is that right? If so, that's very disappointing.

So you just have to describe the typings the same way you call your factory function:

function baz(fooType: <T>(bar: T) => Foo<T>) {

  let foo1 = new fooType<number>(1);

  let foo2 = new fooType<string>("2");

}

Note:

Knowing that it uses a dependency injection mechanism was in fact quite important since that solves the issue of the generic declaration. However <T> means that typeof T equals any. You should specify something more accurate like <T: number | string>.