CODEWITHSUNDEEP
angularionic2observablesubscribe
mikro098
mikro098

Reputation: 2343

How to wait for return value and subscribe to it in Angular2?

I've encountered a problem while developing app in Ionic. I'm executing a query on the database using database provider and it is fine but it is probably called asynchronous because I get undefined.

After some checks and other logic I'm returning value from the database:

this.databaseProvider.getValueFor(saved.id)
    .then(data => {
           return data;
    });

Is there any way to return data to Observable and subscribe to it? I'm quite new to Angular2 and don't know all concepts.

Upvotes: 0

Views: 3275

Answers (2)

Kooldandy
Kooldandy

Reputation: 555

Observables are lazy so you need to subscribe it to get the data from it.

this.databaseProvider.getValueFor(saved.id)
  .subscribe(data => {
       console.log(data); //response
});

getValueFor(id): Observable<any> { const url = 'http://yourAPI/'+id; return this.http.get<any>(url) .pipe( map((res: any) => res.json()), catchError(e => this.handleError(e)) ); }

Upvotes: 0

Pankaj Parkar
Pankaj Parkar

Reputation: 136134

You can use [**Observable.fromPromise**][1] method to convert promise to Observable & then subscribe to Observable to retrieve data from it.

SomeMethod(){
   return Observable.fromPromise(this.databaseProvider.getValueFor(saved.id))
}

//Usage
this.SomeMethod().subscribe(data => {
   console.log("data", data)
})

Upvotes: 1

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