Rails Console

Destroy and rebuild the database with simple data

rails test:wipe

Enter Rails Console

rails c

Show which albums this Artist has

Artist.first.albums

Show the tracks from within an album

Artist.first.albums.first.tracks

Show the name of the song starting from Artist > Album > Track > Song

Artist.first.albums.first.tracks.first.song.title

Find the artist this songs belongs to

Song.first.artist

Get the album a song belongs to

Song.first.track.album

Get the tracks from a specific album

Album.second.tracks

Show the artist this album belongs to

Album.first.artist

Find the songs with the title "Sad But True"

Song.where("title = 'Sad But True'", Song.pluck(:title))

Find the songs with the text "sad" within the title

Song.where("title ILIKE ?", "%sad%")

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Goals

• An artist has many songs <> Songs belong to artists
• An artist has many albums <> Albums belong to artists
• An album has many tracks <> Tracks belong to albums <> Tracks have one song
• Songs belong to many albums through tracks

I want to be able to:

• Access an artist starting with a song

Song.first.artist

• Access an album starting from a song

Song.find_by_title("Enter Sandman").tracks.first.album

• Access a song starting from a artist

Artist.find_by_name("Metallica").albums.first.tracks.first.song

• Access a track's order starting from a song

Song.first.albums.first.tracks.first.order

• Access all the albums this song can be found on

Song.first.albums

Alternative Method

Song.first.tracks.album

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Resources

• https://gorails.com/episodes/comments-with-polymorphic-associations

• http://railscasts.com/episodes/154-polymorphic-association

• http://6ftdan.com/allyourdev/2015/02/10/rails-polymorphic-models/

• https://www.sitepoint.com/brush-up-your-knowledge-of-rails-associations/

• http://6ftdan.com/allyourdev/2015/02/10/rails-polymorphic-models/

• http://6ftdan.com/allyourdev/2014/08/01/manual-polymorphic-creation-in-rails/

• https://github.com/danielpclark/PolyBelongsTo

• PolyBelongsTo gem