Adding a column to an existing table in a Rails migration

Question

I have a Users model which needs an :email column (I forgot to add that column during the initial scaffold).

I opened the migration file and added t.string :email, did rake db:migrate, and got a NoMethodError. Then I added the line

add_column :users, :email, :string 

again rake db:migrate, again NoMethodError. Am I missing a step here?

Edit: here's the migration file.

class CreateUsers < ActiveRecord::Migration     def self.up       add_column :users, :email, :string       create_table :users do |t|         t.string :username         t.string :email         t.string :crypted_password         t.string :password_salt         t.string :persistence_token          t.timestamps       end     end      def self.down       drop_table :users     end   end 

Answer 1

If you have already run your original migration (before editing it), then you need to generate a new migration (rails generate migration add_email_to_users email:string will do the trick). It will create a migration file containing line: add_column :users, email, string Then do a rake db:migrate and it'll run the new migration, creating the new column.

If you have not yet run the original migration you can just edit it, like you're trying to do. Your migration code is almost perfect: you just need to remove the add_column line completely (that code is trying to add a column to a table, before the table has been created, and your table creation code has already been updated to include a t.string :email anyway).

Answer 2

Use this command on the terminal:

rails generate migration add_fieldname_to_tablename fieldname:string 

and

rake db:migrate 

to run this migration