I'm trying to get the information received via JSON, but I can't access it. The data arrives, as shown in the image below: screenshot from Console

When I tried to access any property from it, I received "undefined" or "Property 'name' does not exist on type 'Track[]'".

track.service.ts:

export class TrackService {

  constructor(private httpClient: HttpClient) { }

  private TracksUrlPre: string = 'https://ws.audioscrobbler.com/2.0/?method=geo.gettoptracks&country=';
  private TracksUrlPos: string = '&api_key=78769e93e4d6f4576ee0a1cc572f84dc&format=json';

  retrieveAll(): Observable<Track[]> {
    return this.httpClient.get<Track[]>(`${this.TracksUrlPre}brazil${this.TracksUrlPos}`, {responseType: 'json'});
  }
  
}

track-list.component.ts:

export class TrackListComponent implements OnInit {

  constructor(private trackService: TrackService) { }

  _tracks: Track[] = [];
  //_tracks2: Track[] = [];

  ngOnInit(): void {
    this.trackService.retrieveAll().subscribe(
      track => { 
        this._tracks = track;
        console.log(this._tracks.name); // Output: Property 'name' does not exist on type 'Track[]'
      })
  }
}

track.ts:

export interface Track {
  tracks: {
    "track": [
      {
        "name": string,
        "duration": number,
        "listeners": number,
        "mbid": string,
        "url": string,
        "streamable": {
          "#text": number,
          "fulltrack": number
        },
        "artist": {
          "name": string,
          "mbid": string,
          "url": string
        },
        "image": [
          {
            "#text": string,
            "size": string
          },
          {
            "#text": string,
            "size": string
          },
          {
            "#text": string,
            "size": string
          },
          {
            "#text": string,
            "size": string
          }
        ],
        "@attr": {
          "rank": number
        }
      }
    ],
    "@attr": {
      "country": string,
      "page": number,
      "perPage": number,
      "totalPages": number,
      "total": number
    }
  }
}

I tried this._tracks.name, this._tracks.tracks.name, this._tracks[0], this._tracks[0].name. I think maybe the problem is the way to access the properties inside "tracks" in the hierarchy or the data is not being allocated in the _tracks array.

CodePudding user response：

1. The API returns a response with the Track type. In the retrieveAll method, it should return an Observable of Track type.

track.service.ts

retrieveAll(): Observable<Track> {
  return this.httpClient.get<Track>(
    `${this.TracksUrlPre}brazil${this.TracksUrlPos}`,
    { responseType: 'json' }
  );
}

2. Declare a _track variable with Track type.

_track: Track;

3. Assign the track value received from retrieveAll method to _track. To get the first name of the item, use this._track.tracks.track[0].name.

this.trackService.retrieveAll().subscribe((track) => {
  this._track = track;

  console.log(this._track.tracks.track[0].name);
});

Demo @ StackBlitz

CodePudding user response：

this.trackService.retrieveAll().subscribe(
 tracks => { 
    this._tracks = tracks; // array of Tracks, not Track
    this._tracks.map(track => console.log(track.name)) // Track will be here   
 });

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