Question

Thanks for any help in advance.

I would like to set id3 tag data in my database as attributes for my model MasterSong. Specifically, title, artist, and album.

create_table :master_songs do |t|
  t.integer :user_id
  t.has_attached_file :m_song
 **- t.string :title
 - t.string :artist
 - t.string :album**

In my model I’m using a callback to set the data before the object(master_song) is saved.

before_save :set_id3_tags_in_database

def set_id3_tags_in_database
TagLib::MPEG::File.open(self.m_song.path) do |file|
   tag = file.id3v2_tag
   tag.title
   tag.album
   tag.artist
end
  self.update_attributes(:title => tag.title,
  :artist => tag.artist,
  :album => tag.album)
end

I’m pretty sure my syntax is the problem. The object seems to hit an error

undefined method `title' for nil:NilClass with an infinite loop

Controller create action is normal:

 def create
   @master_song = current_user.master_songs.build(params[:master_song])

   respond_to do |format|
    if @master_song.save
     format.html { redirect_to @master_song, notice: 'Master song was successfullycreated.' }
   end

What am I doing wrong here?
Update:
def set_id3_tags
z = TagLib::MPEG::File.open(self.m_song.path) do |file|
tag = file.id3v2_tag
tag.title
end
self.update_attribute!(:title => z)
end

get stack level too deep error now.

Answer 1

OK! So I did it, after playing and playing and playing.

def set_id3_tags
z = TagLib::MPEG::File.open(self.m_song.path) do |file|
 unless tag.nil?
  tag = file.id3v2_tag
  self.title = tag.title
  self.album = tag.album
  self.artist = tag.artist

  else
end

end

Adding the if title.nil? did it for me. Callbacks are weird but definitely valuable. Hope this helps someone else.