Wait for inner subscriptions inside map?

Question

When I try to subscribe inside map function, the observable doesn't wait for inner subscriptions to execute.

I have the folowwing :

        return this.http.get(url).map((project)=>{       
             // replace pilot id by pilot object 
             this.UserService.retrieveObject(project.pilot).subscribe(pilot => { 
                 project.pilot = pilot,
             })

             //replace owner id by owner object
             this.UserService.retrieveObject(project.owner).subscribe(owner => { 
                 project.owner = owner,
             })
             return project;
         });

the returning project object contains owner, and pilot ids instead of objects because it doesn't wait for subscriptions.

How to make so that observable wait for all inner subscriptions to finish ?

https://stackoverflow.com/questions/40788163/how-to-make-nested-observable-calls-in-angular2 — Dionisis K, Mar 09 '18 at 13:02

score 3 · Accepted Answer · answered Mar 09 '18 at 13:00

3

You'll need to refactor this significantly.

You can use forkJoin to wait for both Observables to complete and then use its "projection" function to update project object:

return this.http.get(url)
    .mergeMap(project => Observable.forkJoin(
        this.UserService.retrieveObject(project.pilot),
        this.UserService.retrieveObject(project.owner),
        (pilot, owner) => {
            project.pilot = pilot;
            project.owner = owner
            return project;
        }
    ));

answered Mar 09 '18 at 13:00

martin

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One thing worth pointing out is the error behavior: if either sub-request fails, the overall chain will fail. – Ingo Bürk Mar 09 '18 at 13:29
I love you man, I would never guess the role of the last forkJoin parameter without your answer. TY VM – a bsss Mar 09 '18 at 13:32
@IngoBürk How to make so that it executes even if one request fail ? – a bsss Mar 09 '18 at 13:37
You can add a `.catch(…)` to the requests inside `forkJoin` to handle errors in individual sub-requests. – Ingo Bürk Mar 09 '18 at 13:38

Wait for inner subscriptions inside map?

1 Answers1