Migration error when adding a column to an existing table

Question

I'm trying to add a users username to a song.

app/models/user.rb

class User < ActiveRecord::Base
  has_many :songs 
  ...
end

app/models/song.rb

class Song < ActiveRecord::Base
  belongs_to :user
  ...
end

I'm trying to make a migration to add a username table to my songs table

class AddUsernameToSongs < ActiveRecord::Migration
  def change
    add_column :songs, :username, :string
  end
end

But I keep getting an uninitialized constant error when I try to run rake db:migrate

I want to be able to on each song call

<%= song.username %>

To post the author of the track.

I'm using devise to set up my users and the devise table already has a username field.

Post your full migration error and the filename of your migration. Lastly, song.username isn't magic. You need to be sure you assign a value to that attribute. — Wes Foster
– Wes Foster, Commented Feb 17, 2016 at 2:36
Your belongs_to :user line in song.rb is going to assume you have a user_id column on the songs table. Do you have this foreign key column? — ajporterfield
– ajporterfield, Commented Feb 17, 2016 at 3:09
Don't add a username column to your song table. If you have the relation setup correctly, you should be able to access the username by doing song.user.username — dan-klasson
– dan-klasson, Commented Feb 17, 2016 at 3:17

MZaragoza · Accepted Answer · 2016-02-17 20:39:36Z

1

Its a better idea to link to the song to a user by id than just the username.

if you don't already have this. I think that you do as you say you have an association.

class AddUserToSongs < ActiveRecord::Migration
  def change
    add_column :songs, :user_id, :integer
  end
end

In your song model you can add a method called ** author **

class Song < ActiveRecord::Base
  belongs_to :user
  ...
  def author
    user.name # this can be username or what ever field in the user's table you want 
  end
end

Now in your views you can do something like this.

- songs.each do |song|
  = song.author
  %br

I hope that this helps. Happy Hacking

edited Feb 17, 2016 at 20:39

answered Feb 17, 2016 at 3:42

MZaragoza

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