Fulfill several promises and execute an HTTP request in Angular 2

At this moment, I am in need of retrieving two elements from my storage, each providing me with a promise. The challenge lies in using these promises to create an HTTP request in Angular 2. Despite numerous attempts, I have been unsuccessful in finding the right approach, always resulting in an

Observable<Observable<Response>>
.

    let tokenPromise = this.getToken()
    let registrationTokenPromise = this.getRegistrationToken()

    Observable.zip(
        tokenPromise,
        registrationTokenPromise,
        (token, registrationToken) => {
            let headers = this.headers(token)
            return this.http.post(`${this.apiBase}/users/registration-token`,
                { registration_token: registrationToken },
                headers
            )
        })

My query now remains: How can I resolve this issue to successfully obtain an Observable<Response>?

Answer №1

When you receive an

Observable<Observable<Response>>
, it is because the Observable.zip function returns an Observable and the http.post function also returns an Observable. To access the actual response, you will need to use the subscribe method on the Observable.zip result.

Observable.zip(
        tokenPromise,
        registrationTokenPromise,
        (token, registrationToken) => {
            let headers = this.headers(token)
            return this.http.post(`${this.apiBase}/users/registration-token`,
                { registration_token: registrationToken },
                headers
            )
        })
        .subscribe(response => {
           //do something with response
        })

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