table relations and record creation

rubyonrails-talk
1

I have a situation where I have three models, Album, Artists and Songs: class Album < ActiveRecord::Base   belongs_to :song end

class Artist < ActiveRecord::Base   belongs_to :song end

class Song < ActiveRecord::Base   belongs_to :artist end

So, an album can have songs that have artists.

The problem is that on the Album create form, the user is allowed to enter all three values. So, the user may enter an existing album that has a new song by a new artist. Or they have enter a new album that has an existing song by an existing artist.

I can't figure out how to manage this create in the controller. So, far I have: def create     @artist = Artist.find_or_create_by_name(params[:artists][:name])

    @song = Song.find_by_name(params[:songs][:name])     if @song.nil?           @song = Song.new(:name => params[:songs][:name], :artist_id => @artist.id)           if !@song.save             flash[:error] = "Couldn't create song"                   redirect_to :action => 'new'           end     end

    @album = Album.new()     @album.item_id = @item.id     @album.song_id = @song.id     if @album.save       flash[:notice] = 'Album was successfully created.'       redirect_to :action => 'show', :id => @album.id     else       render :action => 'new'     end end

This seems to work, but it feels kludgy and I'm not sure if there is another, more Rails appropriate way to do it. Any suggestions?

2

uhm your code is a bit confusing ...

1) where does @item come from? it's not created in the "create" action... some before filter? what is it? 2) you say users can enter an existing album, but you always create a new one ? and doesn't it get a name or something? 3) how are your associations set up?

while because of the above, i'm not sure what you exactly want or need, i was in the mood to type some stuff out as i like associations problems. If it doesn't suit your needs exactly maybe you can get some hints out of it:

First the associations, i guess how you have (or should have) set them up, due to above unclarities:

lass Artist < ActiveRecord::Base   has_many :songs   has_many :albums, :through => :songs end

class Song < ActiveRecord::Base   belongs_to :artist   has_many :album_appearances   has_many :albums, :through => :album_appearances end

class AlbumAppearances < ActiveRecord::Base   belongs_to :album   belongs_to :song end

class Album < ActiveRecord::Base   has_many :songs   has_many :artists, :through => :songs end so the association works like this

Artist<->song<->song_appearance<->album

3

That does help. I didn't know about the :through and I didn't think to use an association table. Thanks for the help.

4

Glad i could help.

One more thing:

the "has many :albums" in the Artist class won't work i guess, it slipped in there accidentally. :wink: The rest should be fine though.