find_or_create_by_name with has_many :through - ruby-on-rails

Question

Artists have many Events. Events have many Artists. The join between these two models is called Performances.
I'm trying to associate Artists with Events on the Event add/edit page. I would like to be able to add an Artist only if it doesn't exist, and create the join (performance) regardless. An Artist should be associated with an Event only once.
It was suggested that I use find_or_create_by_name instead of accepts_nested_attributes_for.
I'm following the Railscasts #102 instructions for Auto-Complete which say to use virtual attributes. I haven't even gotten to the auto-complete part, just trying to get find_or_create_by_name working.
I'm getting "undefined method `artist_name' for #" on the Event edit and new pages. In the Railscast, Ryan gets an undefined method before he adds the methods to the model. But I have the method in the Model.
No idea what to do.
event.rb
validates_presence_of :name, :location
validates_uniqueness_of :name
validates_associated :performances
has_many :performances, :dependent => :delete_all
has_many :artists, :through => :performances
#accepts_nested_attributes_for :artists, :reject_if => proc {|a| a['name'].blank?}, :allow_destroy => true
def artist_name
artist.name if artist
end
def artist_name=(name)
self.artist = Artist.find_by_name(name) unless name.blank?
end
artist.rb
validates_presence_of :name
has_many :mixes
has_many :performances, :dependent => :delete_all
has_many :events, :through => :performances
perfomance.rb
belongs_to :artist
belongs_to :event
events_controller.rb
def create
#event = Event.new(params[:event])
respond_to do |format|
if #event.save
flash[:notice] = 'Event was successfully created.'
format.html { redirect_to(admin_events_url) }
format.xml { render :xml => #event, :status => :created, :location => #event }
else
format.html { render :action => "new" }
format.xml { render :xml => #event.errors, :status => :unprocessable_entity }
end
end
end
_form.html.erb
<% form_for([:admin,#event]) do |f| %>
<p>
<%= f.label :name %><br />
<%= f.text_field :name %>
</p>
<p>
<%= f.label :location %><br/>
<%= f.text_field :location %>
</p>
<p>
<%= f.label :date %><br />
<%= f.date_select :date %>
</p>
<p>
<%= f.label :description %><br />
<%= f.text_area :description %>
</p>
<% f.fields_for :artists do |builder| %>
<%= render 'artist_fields', :f => builder %>
<% end %>
<p><%= link_to_add_fields "Add Artist", f, :artists %></p>
<p>
<%= f.submit 'Submit' %> <%= link_to 'Cancel', admin_events_path %>
</p>
<% end %>
_artist_fields.html.erb
<p class="fields">
<%= f.label :artist_name, "Artist"%><br/>
<%= f.text_field :artist_name %>
<%= link_to_remove_fields "remove", f %>
</p>

Answer 1

Personally I would go back to accepts_nested_attributes_for, ryan bates method there was in the days before nested attributes.
In your controller do something like:
def new
#event = Event.find params[:id]
#artist = #event.artists.build
def edit
#event = Event.find params[:event_id]
#artist = #event.artists.find params[:user_id]
While in the view
...
<% f.fields_for :artists, #artist do |builder| %>
...