TypeScript - Can't "new" an interface for of an existing type

Question

I am trying to use RxJs definitions in TypeScript application I am writing. I imported the defs and now I am trying to new up a subject.

this.stream = new Rx.Subject();

However when I try this I get the following error.

Error 6 The property 'Subject' does not exist on value of type '{ Internals: { inherits(child: Function, parent: Function): Function; addProperties(obj: Object, ...sourcces: Object[]): void; addRef(xs: Rx.IObservable, r: { getDisposable(): Rx._IDisposable; }): Rx.IObservable; }; Observer: { create(onNext: (value: any) => void, onError?: (exception: any) => void, onCompleted?: () => void): Rx.IObserver; fromNotifier(handler: (notification: Rx.INotification) => void): Rx.IObserver; }; }

When I look at the type defs for this I can see that the Subject class has been defined as an interface

export interface Subject {
    (): ISubject;

    create(observer: IObserver, observable: IObservable): ISubject;
}

Can someone tell me how I can create an instance of this Subject class as I cannot find a way to do it. Currently using TS 9.1.1. I thought the (): ISubject might do it but doesn't seem to have any impact.

I know some suggestions are to define a class instead but then I would need to implement all the methods from the base interfaces so this would be huge as it inherits from IObservable.

Answer 1

Using the latest version of the rx.js typing from Definitely Typed this works. Updating your definition is the way to go.

You can also try it on the TypeScript Playground - you'll need to paste in the code from Definitely Typed to test it out (long-links to the playground no longer seem to be allowed on here).

var x = new Rx.Subject();