ruby on rails - How to populate a dropdown [rails4] -

so, have app lets users upload , comment on songs. however, i'd add genres category. when users upload songs they'll able choose genre of song. when add search.

for quick overview of code see: www.github.com/apane/leap

i'm guessing i'd add genres table db , associate songs e.g:

genre belongs_to song, song has_many genres.

but after i'm stumped. how populate genres dropdown?

rails g model genre name rails g model genre_song genre:belongs_to song:belongs_to rake db:migrate 

models/genre.rb

has_many :genre_songs has_many :songs, through: :genre_song 

models/song.rb

has_many :genre_songs has_many :genres, through: :genre_song  def self.tagged_with(name)   genre.find_by_name!(name).songs end  def tag_list   genres.map(&:name).join(", ") end  def tag_list=(names)   self.genres = names.split(",").map |n|     genre.where(name: n.strip).first_or_create!   end end 

songs/index.html.erb

genres: <%= raw song.genres.map(&:name).map { |t| link_to t, genre_path(t) }.join(', ') %> 

songs/_form.html.erb

<div class="field">   <%= f.label :tag_list, "genres (separated commas)" %><br />   <%= f.text_field :tag_list %> </div> 

songs_controller.rb

add tag_list permited params