TypeScript: Create function wrapper for class constructor

Question

I am trying to create a function that takes a Class and returns function that can return the Class instance. However, it provides type information only for the base class and have an error when I try to create an instance in createFactory function. Playground

class BaseStore {
  public id = 1;
}

class OneStore extends BaseStore {
  public action() { }

  constructor(public a: string, public b: number) {
    super()
  }
}

function createFactory<T extends BaseStore, C extends new (...args: any) => T>(Create: C) {
  return (...args: ConstructorParameters<C>) => new Create(...args);
}

const oneFactory = createFactory(OneStore);
const one = oneFactory('s', 2);
one.id
one.action();

Titian Cernicova-Dragomir · Accepted Answer · 2020-06-08 15:47:36Z

1

Typescript can't really resolve conditional types that still contain unresolved type parameters. You could write the types in a different way:

function createFactory<T extends BaseStore, P extends any[]>(Create: new (...args: P) => T) {
  return (...args: P) => new Create(...args);
}

Playground Link

answered Jun 8, 2020 at 15:47

Titian Cernicova-Dragomir

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