Adding permissions to mixtapes

gistfile1.rb

#Mixtape Controller


def share  
    @mixtape = Mixtape.find(params[:id])
    @shared_user = User.find(params[:user])
    @shared_permission = params[:permission].to_sym 
    
    @mixtape.add_user(@shared_user, @shared_permission) if @mixtape.user_mixtapes.find_by_user_id_and_permission(@shared_user,@shared_permission)
    
    redirect_to :back, :notice => "Added #{@shared_user.email} with the permission #{@shared_permission}"
   
end



#Mixtapes Show View (form only)


<% permission_types = UserMixtape::Permissions.map{|a| a } %> 
<%= form_tag mixtapes_share_path(@mixtape)  do  %>   
  <%= select_tag("user", options_from_collection_for_select(@users, "id", "email")) %>
  <%= select_tag("permission", options_from_collection_for_select(permission_types, :first, :first)) %>
  <%= submit_tag("Share") %>
<% end %>  


#User_mixtape model

class UserMixtape < ActiveRecord::Base
  Permissions = {:owner => 0, :collaborator => 1, :listener => 2} 

...

end

#routes.rb (relevant)

post 'mixtapes/:id/share' => 'mixtapes#share', :as => "mixtapes_share"