How specify class definition as parameter type in Typescript

Question

I would like to pass type information for class, with hinting the compiler that the given parameter is not an instance of a class but the class definition. How can I do that?

import * as Routes from '../routes';
import * as Entities from '../entities';

export class RouteManager {
  public router = Router();
  private connection = getConnectionManager().get();

  constructor() {
    this.addRoute(Routes.VideoRoute, Entities.Video);
  }

  addRoute(routeClass: AbstractRoute<AbstractEntity>, entity: AbstractEntity): void {
    const instance = new routeClass(entity, this.connection.getRepository(entity))
    this.router.get(instance.route, instance.find);
  }
}

Here the compiler complains about the new routeClass(entity, this.connection.getRepository(entity)) line because it thinks routeClass is an instance of AbstractRoute<AbstractEntity> and not the exported class definition for it.

I have tried usingAbstractRoute<AbstractEntity>.constructor but Typescript doesn't seem to know this structure.

Answer 1

The syntax for this looks a little bit weird. Basically you define a signature that uses something like new(...args: any[]) => T. You of course can be more strict by replacing T with your class and the args with the constructor signature.

I would recommend something like this:

class Foo {}
type Constructor<T> = new(...args: any[]) => T;

function createFoo(thing: Constructor<Foo>) { return new thing(); }