Creating multiple habtm relationships with two models in one request - ruby-on-rails

Question

I currently have an Album/Artist database that uses multiple join tables to signify when how an artist relates to the album. They can be listed as a Composer, an Arranger, or a Performer. That is:
class Artist < ActiveRecord::Base
...
has_and_belongs_to_many :albumbycomposers, :class_name => "Album", :join_table => "albums_composers"
has_and_belongs_to_many :albumbyarrangers, :class_name => "Album", :join_table => "albums_arrangers"
has_and_belongs_to_many :albumbyperformers, :class_name => "Album", :join_table => "albums_performers"
...
end
And
class Album < ActiveRecord::Base
has_and_belongs_to_many :composers, :class_name => "Artist", :join_table => "albums_composers"
has_and_belongs_to_many :arrangers, :class_name => "Artist", :join_table => "albums_arrangers"
has_and_belongs_to_many :performers, :class_name => "Artist", :join_table => "albums_performers"
...
end
This code is used to look up for existing artists in the database, then create the association. If no artist exists, then I use the .build method to create the artist.
class AlbumsController < ApplicationController
...
def create
#album = Album.new(params[:album])
params["Composer Names"].each do |each|
if each.empty? == false
#exists = Artist.find_by_name(each)
if #exists.nil? == true
#album.composers.build(:name => each)
else
#album.composers << Artist.find_by_name(each)
end
end
end
params["Arranger Names"].each do |each|
if each.empty? == false
#exists = Artist.find_by_name(each)
if #exists.nil? == true
#album.arrangers.build(:name => each)
else
#album.arrangers << Artist.find_by_name(each)
end
end
end
...
end
...
end
The problem I encounter occurs when I try to enter a new artist as both a composer and an arranger. For example, say I submit this as a post request
Parameters: {"Name"=>["New Album"],
"Performer Names"=>["New Artist"],
"Composer Names"=>["New Artist"],
"Arranger Names"=>["New Artist"],
...
}
Since the composer arguments are first, rails interprets them properly (as if the artist does not exist). The arranger and performer arguments are also interpreted as if the artist does not exist. Then rails begins inserting data into my database. First the album is created and inserted into the albums table, then "New Artist" is created and inserted into album_composer (according to the .build method).
However, for the arranger and performer arguments, the build method can no longer be used, since the artist has been created, so the code is not executed properly.
I tried to workaround by using the push method (aka <<) in the arranger and performer argument lines for this specific case, but that doesn't work because it instantly fires without waiting for the artist to be made by the composer argument, resulting in an "Artist cannot be found" error. For Reference:
collection<<(object, …)
Adds one or more objects to the collection by creating associations in the join table (collection.push and collection.concat are aliases to this method).
Note that this operation instantly fires update sql without waiting for the save or update call on the parent object.
What is the proper way to handle this?

Answer 1

I solved the problem by adding in each artist separately into my database first using the code:
#artists = params["Composer Names"] | params["Arranger Names"] | params["Performer Names"]
#artists.each do |artist|
if artist.empty? == false
#exists = Artist.find_by_name(artist)
if #exists.nil?
#artist = Artist.new(:name => artist)
#artist.save
end
end
end
I could use the push method and add each artist to the proper join table using code like:
params["Composer Names"].each do |each|
if each.empty? == false
#album.composers << Artist.find_by_name(each)
end
end
so that's that!