Garrett Sanderson Garrett Sanderson - 2 months ago 9
AngularJS Question

Getting Nested Data From JSON Object in Angular 2

Hello I am building something similar to a music player app. I have a service set up grabbing the data from a JSON file that I have in a fixture. I can grab all top level data with *ngFor but once I start to ask for something like songs.parts.name this shows up undefined.

I have the *ngFor spitting out the top level key value pairs on a page and then I would like to be able to click on a specific song name and have it filter the data to find the correct song url.

How can I loop through that array and grab those objects?

Any help would be much appreciated.

JSON

{
"songs": [
{
"name": "America The Beautiful",
"difficulty": "Medium",
"time": "3:38",
"hasPianoWords": true,
"hasPianoSolfa": false,
"hasTrackWords": false,
"parts": [
{
"name": "Baritone",
"urls": {
"pianoWords": "http://www.taabc.org/check-off-songs/baritone/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"pianoSolfa": "http://www.taabc.org/check-off-songs/baritone/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"trackWords": "http://www.taabc.org/check-off-songs/baritone/america-the-beautiful/america-the-beautiful-piano-words.mp3"
}
},
{
"name": "Bass",
"urls": {
"pianoWords": "http://www.taabc.org/check-off-songs/bass/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"pianoSolfa": "http://www.taabc.org/check-off-songs/bass/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"trackWords": "http://www.taabc.org/check-off-songs/bass/america-the-beautiful/america-the-beautiful-piano-words.mp3"
}
},
{
"name": "Second Tenor",
"urls": {
"pianoWords": "http://www.taabc.org/check-off-songs/second-tenor/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"pianoSolfa": "http://www.taabc.org/check-off-songs/second-tenor/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"trackWords": "http://www.taabc.org/check-off-songs/second-tenor/america-the-beautiful/america-the-beautiful-piano-words.mp3"
}
},
{
"name": "First Tenor",
"urls": {
"pianoWords": "http://www.taabc.org/check-off-songs/first-tenor/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"pianoSolfa": "http://www.taabc.org/check-off-songs/first-tenor/america-the-beautiful/america-the-beautiful-piano-words.mp3",
"trackWords": "http://www.taabc.org/check-off-songs/first-tenor/america-the-beautiful/america-the-beautiful-piano-words.mp3"
}
}
]
}
]
}


Songs.Service.ts

export class SongService {
constructor(private _http: Http) {}

getAllSongs() {
return this._http.get('/fixtures/songs.json')
.map((response: Response) => response.json().songs)
.toPromise()
.catch(this.handleError);
}

getSongByName(songName:string) {
return this._http.get('/fixtures/songs.json')
.map((response: Response) => _.find(response.json().songs, {'name': songName}))
.toPromise()
.catch(this.handleError);
}


Song Component

export class SongsComponent {
public songs: any;
public activeSong: any;
public activeSongURL: any;

constructor(private _songsService: SongService, private router: Router, private route: ActivatedRoute) {
}

ngOnInit() {
this._songsService.getAllSongs().then(result => {
this.songs = result;
console.log('Songs: ', this.songs);
});
}

playSong(songName:string) {
console.log('clicked song:', songName)

this._songsService.getSongByName(songName).then(result => {
this.activeSong = result;
console.log('active song', this.activeSong);
this.activeSongURL = this.activeSong.baritone.pianoWords;
console.log(this.activeSongURL);
})
}

selectSong(songName:string) {
this.router.navigate(['/song'], songName);
}
}


HTML Template

<section class="songs container">
<div class="song col-md-3" *ngFor="let song of songs">
<h4 (click)="selectSong(song.name)">{{song.name}}</h4>
<span>Difficulty: {{song.difficulty}}</span>
<span>Time: {{song.time}}</span>
<span><strong>Baritone</strong></span>
<span *ngIf="song.hasPianoSolfa" class="piano-solfa"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Piano Solfa</span>
<span (click)="playSong(song.name)" *ngIf="song.hasPianoWords" class="piano-words"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Piano Words</span>
<span (click)="playSong(song.name)" *ngIf="song.hasTrackWords" class="track-words"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Track Words</span>
</div>
</section>

<section class="audio-player">
<audio src="{{activeSongURL}}" autoplay controls="controls">
Your browser does not support the <code>audio</code> element.
</audio>
</section>

Answer

You could make use of Safe-Navigation-Operator

Looks like you might of had it or been close to having it, shouldn't it be somehting like

<section class="songs container">
    <div class="song col-md-3" *ngFor="let song of songs">
        <h4 (click)="selectSong(song.name)">{{song.name}}</h4>
        <span>Difficulty: {{song.difficulty}}</span>
        <span>Time: {{song.time}}</span>

        <div *ngIf="song?.parts.length > 0">

            <div *ngFor="let part of song?.parts">
                <strong>{{ part.name }}</strong>
                <span class="piano-words" (click)="playSong(song.name)"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Piano Words</span>
                <span class="piano-solfa" (click)="playSong(song.name)"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Piano Solfa</span>
                <span class="track-words" (click)="playSong(song.name)"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Track Words</span>
            </div>

        </div>

        <!-- <span><strong>Baritone</strong></span>
        <span *ngIf="song.hasPianoSolfa" class="piano-solfa"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Piano Solfa</span>
        <span (click)="playSong(song.name)" *ngIf="song.hasPianoWords" class="piano-words"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Piano Words</span>
        <span (click)="playSong(song.name)" *ngIf="song.hasTrackWords" class="track-words"><i class="fa fa-play-circle-o" aria-hidden="true"></i>Track Words</span>
    </div> -->
</section>