Add track/{new,create} with file upload for the track

app/models/track.rb

@@ -1,3 +1,17 @@
 class Track < ActiveRecord::Base
   validates_presence_of :name
+
+  after_create :save_file
+
+  def uploaded_file=(file)
+    @file = file
+  end
+
+  def save_file
+    if @file
+      File.open("#{Rails.root}/data/tracks/#{id}", 'w') do |f|
+        f.write @file.tempfile.read
+      end
+    end
+  end
 end