CODEWITHSUNDEEP
javaandroidrealm
Ahorner
Ahorner

Reputation: 214

RealmResult Many-Many Relationship With Adapter

I have two models who (with relevant properties) look like this:

Playlist.java

@PrimaryKey
String id;
String name;
RealmList<Song> songs;

Song.java

@PrimaryKey
String id;
String name;

As you can see, a playlist can contain many songs, and a song can belong to many playlists.

In one portion of my app I am displaying all the songs in a RecyclerView with a RealmBaseAdapter. I accomplish this no problem with:

RealmResults<Song> songResult = realm.where(Song.class).findAll();
RealmSongsAdapter realmAdapter = new RealmSongsAdapter(getActivity().getApplicationContext(), songResult , true);
songAdapter.setRealmAdapter(realmAdapter);

My question is: how would I go about showing songs for only a certain playlist? Since Song.java has no reference to it's own playlists, I don't have a way to get a RealmResult based off the Playlist object. Ideally I would like something like:

Playlist playlist = realm.where(Playlist.class).equalTo("id", playlistID).findFirst();
RealmResults<Song> playlistSongs = playlist.getSongs();

But playlist.getSongs() returns a RealmList<Song> rather than a RealmResult<Song>.

One solution I found would be to create a RealmQuery based on the Song ids in the playlist, but that seems counter intuitive:

RealmQuery<Song> query = mRealm.where(Song.class);
for (Song song : playlist.getSongs()) {
    query = query.or().equalTo("id", song.getId());
}
RealmResults<Song> results = query.findAll();

The other problem with this is I would have to re-create this query every time the playlist song list changes.

Is there an easier way? Thanks in advance!

Upvotes: 4

Views: 983

Answers (1)

Christian Melchior
Christian Melchior

Reputation: 20126

Christian from Realm here. Currently there is unfortunately no other way than the one you found yourself if you don't want to maintain a RealmList<Playlist> field on the Song. That said we have a concept called Backlinks on our TODO which are exactly for use cases like this: https://github.com/realm/realm-java/issues/607

Upvotes: 1

Related Questions