Angular2：承诺中的回归观察

Question

i have the following code.

getListCategoryOfQuestion() {
    return this.authService.getToken()
        .then(token => {
            let headers = new Headers();
            headers.append('Authorization', `Bearer ${token}`);
            return this.http.get('http://localhost:3333/question/getCategories', {headers:headers})
                .map(res => res.json())
                .catch(this.handleError);
        })
        .catch(this.handleError);
}

I know that I can't return sync value from promise, but observable are async. The return of this function is of type Promise<Observable< > >

I just want to know how to subscribe to this observable, at the moment i have tried this:

loadCategory(){
    this.questionDBService.getListCategoryOfQuestion()
        .subscribe(data => {
            this.categories = data;
            console.log(data);
        });
}

But of course it's not working because the result is not an observable, so anyone know how manage this problem ?

Answer 1

A promise with observable... that's nice :) try this:

loadCategory(){
    this.questionDBService.getListCategoryOfQuestion().then((observer) => {

         observer.subscribe((data) => {
            this.categories = data;
            console.log(data);
        });

    });

}