Angular map http response value with another http call

Question

I have an http call that looks like this :

public getCommuneByCode(code: string): Observable<Commune> {
  return this.http.get<Commune[]>(ApiUrl);
}

And the the Commune model as follow :

export interface Commune {
  code: string;
  departement: string;
  postalCode: string;
}

I have another http call to get a user data :

public getUserData(id: number): Observable<User> {
  return this.http.get<User>(ApiUrl);
}

User model :

export interface User {
  id: number;
  name: string;
  libAddress: string;
}

Want I to do is to set the libAddress property with the response of the getCommuneByCode service like this :

this.service.getUserData(id).pipe(
    map((user: User) => {
      user.libAddress = this.service.getCommuneByCode(code).pipe(
        map(commune => `${commune.postalCode} - ${commune.departement}`)
      );
      return user;
    })
  ).subscribe((userWithLibAddress) => {
    // user object with all data and libAddress property is equal to ex: 99999 - DepartementXX
  })

But as I expected it's returning an observable of the answer and I'm not sure how to do it to get the answer. Thank for your help

score 4 · Accepted Answer · 2019-01-30 09:56:25Z

4

This one should work. If you need explanation, ask for it !

forkJoin(
  this.service.getUserData(id),
  this.service.getCommuneByCode(code)
).pipe(
  map(([user, commune]) => ({ ...user, libAdress: `${commune.postalCode} - ${commune.departement}`})
);

EDIT If you have to make the calls in sequence :

this.service.getUserData(id).pipe(
  switchMap(user => this.service.getCommuneByCode(user.code)).pipe(
    map(commune => ({ ...user, libAdress: `${commune.postalCode} - ${commune.departement}`}))
  )
)

edited Jan 30, 2019 at 9:56

answered Jan 30, 2019 at 9:28

user4676340

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5 Comments

Imad El Hitti Over a year ago

I thought about forkjoin, but the problem is that if getCommuneByCode fail for any reason both of them fail, which is not what I want.

user4676340 Over a year ago

Even without forkJoin, if you have an error then your code won't work. That's the principle of errors, they don't do what you expect. That's why you have operators like catchError, to process errors when they appear. You argument doesn't really add up there, and is sure not a reason to downvote : your question was about composing an object, not about how to manage errors.

Imad El Hitti Over a year ago

I didn't downvote I was surprised like you when I saw it, I like your solution and so I had no reason to down vote. And thank for you answer concerning catchError, in fact it will be handled in the same way with whatever operator I use

user4676340 Over a year ago

Okay, my bad then ! And that's right, you will need the catchError any way. In my opinion, forkJoin is way cleaner than using [merge/switch/concat]Map operators, since they will add an indent level and will produce the same result.

Imad El Hitti Over a year ago

Oh my bad I do remember now why I couldn't use forkJoin actually, I forget to specify my fault, by the code to call the getCommuneByCode service is based on the user service response. I tried to simplify my api for the question but I missed this detail.

Shofol · Accepted Answer · 2019-01-30 09:38:50Z

1

You can use MergeMap. For example you can try something like this-

this.service.getUserData(id).pipe(
    mergeMap( (user:User) => this.service.getCommuneByCode(code).pipe(
        map(commune => user.libAddress = `${commune.postalCode} - ${commune.departement}`)
      )
    )
  ).subscribe();

answered Jan 30, 2019 at 9:38

Shofol

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