Changing Observable of array to observable of single object when using take(1)

Question

I have below code in angular service using firestore, there is not syntax error and it's working fine,

The problem is the returning type, since I am using take(1) I want the return type be Observable<Client>

fetchByUserId(uid: string): Observable<Array<Client>> {
    return this.collection(ref => ref.where(`users.${uid}`, '>', 0))
      .valueChanges()
      .take(1);
  }

I tried using .first() but problem is by using first observable completes and I want to keep streaming.

Take(1) and first() take an emitted 'value' from observables rather than fetching the first element in an emitted 'value'. You need to use map to transform the value of an array to an object. — yeh, Apr 15 '18 at 22:59

Pac0 · Accepted Answer · 2018-04-15T23:03:32.617

1

.first() and .take(1) will actually do (almost) the same thing in your case.

What you want is map the result array to the first element of your array.

You should be able to insert a map like this :

return this.collection(...)
    .map(arr => arr[0])

this is assuming this.collection(...) actually returns an Observable<Array<Client>>, and in this case the result of this map will return an Observable<Client>

edited Apr 15 '18 at 23:03

answered Apr 15 '18 at 23:00

Pac0

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`first` and `take(1)` do [almost the same](https://stackoverflow.com/a/42346203/6680611) thing. – cartant Apr 15 '18 at 23:02
@cartant thank you for clarification, I'll edit this info into my answer – Pac0 Apr 15 '18 at 23:03
@Pac0 thanks, by your solution also there is no reason to use take(1) – Reza Apr 15 '18 at 23:13
exactly ! Glad it helped. – Pac0 Apr 15 '18 at 23:14

Changing Observable of array to observable of single object when using take(1)

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