Selecting only one table in a join query

[thinkpractice]

Hi all,

I'm building a music player in which I use SQLiteData to cache some local data, mainly playlists and songs. I defined the following schema:

import Foundation
import SQLiteData

enum Models
{
    @Table
    nonisolated struct Track: Identifiable
    {
        let id: UUID
        let artistName: String
        let title: String
        let appleMusicId: String
    }

    @Table
    nonisolated struct Playlist: Identifiable
    {
        let id: UUID
        let name: String
        let appleMusicId: String?
    }

    @Table
    nonisolated struct PlaylistTrack: Identifiable
    {
        let id: UUID
        let playlistId: Models.Playlist.ID
        let trackId: Models.Track.ID
    }

}

(note that I needed to put this schema into an enum to prevent namespace clashes with MusicKit)

And I inserted some data into the database using this Schema. Now I'd like to get the Track objects for a certain playlist, but I'm struggling to get the query right. So far I've come up with this, but this doesn't compile:

@Observable
final class PlaylistModel
{
    let playlistId: Models.Playlist.ID
    
    @ObservationIgnored
    @FetchOne
    var playlist: Models.Playlist?
    
    @ObservationIgnored
    @FetchAll
    var tracks: [Models.Track]
    
    var name: String {
        return playlist?.name ?? "Unknown Playlist"
    }
    
    init(playlistId: Models.Playlist.ID)
    {
        self.playlistId = playlistId
        self._playlist = FetchOne(Models.Playlist.where { $0.id.eq(playlistId)})
        
        // How to select only Models.Track here??
        let query = Models.Track
            .join(Models.PlaylistTrack.all) { $0.id.eq($1.trackId) && $1.playlistId.eq(playlistId) }
            .select { $0.0 }
        
        self._tracks = FetchAll(
            query
        )
    }
    
}

Is there a way only to get the first table in the query back here? Or should I define a @Selection struct for this?

kind regards,

Tim

[mbrandonw]

Hi @thinkpractice, what you have is correct, it just seems like there is a compiler bug with doing { $0.0 }. Probably related to parameter packs. But if you spell out the arguments it works:

.select { tracks, _ in tracks }

[thinkpractice]

@mbrandonw thanks so much! That did the trick 😄