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Piping Observables and Returning a Promise

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0

Why does the code below return a promise that contains an observable?

const queryApi = (request: AxiosRequestConfig): Observable<ParsedData> => 
 return new Observable(observer => 
 axios(request).then(response => 
 observer.next(response);
 observer.complete();
 ).catch(error => 
 observer.error(error);
 )
 ).pipe(map(value => 
 const parser = new Parser(name);
 const response = value as AxiosResponse;
 return parser.parse(response.data);
 ));


const sourcePromise: Promise<ParsedData> = queryApi(request, 1).toPromise();
await sourcePromise.then(source$ => 
 source$.subscribe((value: ParsedData) => console.log(JSON.stringify(value, null, 2)));
).catch(error => console.log(error));

I was expecting the code to:

1. Query an API with axios
   


2. Create an observable using the value resolved by axios
   


3. Pipe that observable to a map operator that returns an observable
   


4. Convert return observable to promise
   


5. Resolve promise to expose data.

javascript typescript rxjs

share|improve this question

asked Mar 28 at 20:18

AriAri

1,63577 gold badges2727 silver badges4545 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i tihnk it might have something to do with not being completed but if you want to get a promise anyway why not jsut return a promise in the first place
  
  – jonathan Heindl
  Mar 28 at 20:26
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I haven't used typescript, but it looks like you aren't calling the promise, just referencing it. sourcePromise.then -> sourcePromise().then
  
  – Nathan
  Mar 28 at 20:29
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Are you saying that parser.parse returns an observable?
  
  – Bergi
  Mar 28 at 20:54
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why are you using observables at all here? You're turning a promise into an observable, then turning that back into a promise. Just use promises directly to make your code much simpler.
  
  – Bergi
  Mar 28 at 20:55
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Where exactly in that code does it "return a promise that contains an observable"?
  
  – Bergi
  Mar 28 at 20:56
  

  
  
  
  

add a comment
 | 

0

Why does the code below return a promise that contains an observable?

const queryApi = (request: AxiosRequestConfig): Observable<ParsedData> => 
 return new Observable(observer => 
 axios(request).then(response => 
 observer.next(response);
 observer.complete();
 ).catch(error => 
 observer.error(error);
 )
 ).pipe(map(value => 
 const parser = new Parser(name);
 const response = value as AxiosResponse;
 return parser.parse(response.data);
 ));


const sourcePromise: Promise<ParsedData> = queryApi(request, 1).toPromise();
await sourcePromise.then(source$ => 
 source$.subscribe((value: ParsedData) => console.log(JSON.stringify(value, null, 2)));
).catch(error => console.log(error));

I was expecting the code to:

1. Query an API with axios
   


2. Create an observable using the value resolved by axios
   


3. Pipe that observable to a map operator that returns an observable
   


4. Convert return observable to promise
   


5. Resolve promise to expose data.

javascript typescript rxjs

share|improve this question

asked Mar 28 at 20:18

AriAri

1,63577 gold badges2727 silver badges4545 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i tihnk it might have something to do with not being completed but if you want to get a promise anyway why not jsut return a promise in the first place
  
  – jonathan Heindl
  Mar 28 at 20:26
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I haven't used typescript, but it looks like you aren't calling the promise, just referencing it. sourcePromise.then -> sourcePromise().then
  
  – Nathan
  Mar 28 at 20:29
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Are you saying that parser.parse returns an observable?
  
  – Bergi
  Mar 28 at 20:54
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why are you using observables at all here? You're turning a promise into an observable, then turning that back into a promise. Just use promises directly to make your code much simpler.
  
  – Bergi
  Mar 28 at 20:55
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Where exactly in that code does it "return a promise that contains an observable"?
  
  – Bergi
  Mar 28 at 20:56
  

  
  
  
  

add a comment
 | 

Why does the code below return a promise that contains an observable?

const queryApi = (request: AxiosRequestConfig): Observable<ParsedData> => 
 return new Observable(observer => 
 axios(request).then(response => 
 observer.next(response);
 observer.complete();
 ).catch(error => 
 observer.error(error);
 )
 ).pipe(map(value => 
 const parser = new Parser(name);
 const response = value as AxiosResponse;
 return parser.parse(response.data);
 ));


const sourcePromise: Promise<ParsedData> = queryApi(request, 1).toPromise();
await sourcePromise.then(source$ => 
 source$.subscribe((value: ParsedData) => console.log(JSON.stringify(value, null, 2)));
).catch(error => console.log(error));

I was expecting the code to:

1. Query an API with axios
   


2. Create an observable using the value resolved by axios
   


3. Pipe that observable to a map operator that returns an observable
   


4. Convert return observable to promise
   


5. Resolve promise to expose data.

javascript typescript rxjs

share|improve this question

asked Mar 28 at 20:18

AriAri

1,63577 gold badges2727 silver badges4545 bronze badges

const queryApi = (request: AxiosRequestConfig): Observable<ParsedData> => 
 return new Observable(observer => 
 axios(request).then(response => 
 observer.next(response);
 observer.complete();
 ).catch(error => 
 observer.error(error);
 )
 ).pipe(map(value => 
 const parser = new Parser(name);
 const response = value as AxiosResponse;
 return parser.parse(response.data);
 ));


const sourcePromise: Promise<ParsedData> = queryApi(request, 1).toPromise();
await sourcePromise.then(source$ => 
 source$.subscribe((value: ParsedData) => console.log(JSON.stringify(value, null, 2)));
).catch(error => console.log(error));

share|improve this question

asked Mar 28 at 20:18

AriAri

1,63577 gold badges2727 silver badges4545 bronze badges

share|improve this question

asked Mar 28 at 20:18

AriAri

1,63577 gold badges2727 silver badges4545 bronze badges

asked Mar 28 at 20:18

AriAri

1,63577 gold badges2727 silver badges4545 bronze badges

asked Mar 28 at 20:18

AriAri

1,63577 gold badges2727 silver badges4545 bronze badges

1 Answer
1

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0

// Using rxjs 6
// This should solve your problem.

import axios from 'axios';
import from from 'rxjs';
import map from 'rxjs/operators';

const queryApi = request => from(axios(request)).pipe(map(res => res.data));

//Make sure to subscribe to the observable

share|improve this answer

answered Mar 29 at 1:50

Ayinla AbdulsalamAyinla Abdulsalam

1133 bronze badges

add a comment
 | 

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0

// Using rxjs 6
// This should solve your problem.

import axios from 'axios';
import from from 'rxjs';
import map from 'rxjs/operators';

const queryApi = request => from(axios(request)).pipe(map(res => res.data));

//Make sure to subscribe to the observable

share|improve this answer

answered Mar 29 at 1:50

Ayinla AbdulsalamAyinla Abdulsalam

1133 bronze badges

add a comment
 | 

0

// Using rxjs 6
// This should solve your problem.

import axios from 'axios';
import from from 'rxjs';
import map from 'rxjs/operators';

const queryApi = request => from(axios(request)).pipe(map(res => res.data));

//Make sure to subscribe to the observable

share|improve this answer

answered Mar 29 at 1:50

Ayinla AbdulsalamAyinla Abdulsalam

1133 bronze badges

add a comment
 | 

// Using rxjs 6
// This should solve your problem.

import axios from 'axios';
import from from 'rxjs';
import map from 'rxjs/operators';

const queryApi = request => from(axios(request)).pipe(map(res => res.data));

//Make sure to subscribe to the observable

share|improve this answer

answered Mar 29 at 1:50

Ayinla AbdulsalamAyinla Abdulsalam

1133 bronze badges

// Using rxjs 6
// This should solve your problem.

import axios from 'axios';
import from from 'rxjs';
import map from 'rxjs/operators';

const queryApi = request => from(axios(request)).pipe(map(res => res.data));

//Make sure to subscribe to the observable

share|improve this answer

answered Mar 29 at 1:50

Ayinla AbdulsalamAyinla Abdulsalam

1133 bronze badges

answered Mar 29 at 1:50

Ayinla AbdulsalamAyinla Abdulsalam

1133 bronze badges

answered Mar 29 at 1:50

Ayinla AbdulsalamAyinla Abdulsalam

1133 bronze badges