undefined local variable or method `confirmed_at' for #User

I am using Rails 3. There is a possible duplicate here. But it did not solve my problem, neither did any other solution.

My migration is as follows

class AddConfirmableToDevise < ActiveRecord::Migration
  def change
    change_table(:users) do |t| 
      t.confirmable 
    end
    add_index  :users, :confirmation_token, :unique => true 
  end
end

I do have devise :confirmable added in User model.

My rake db:migrate gives no output. and my sign up page gives the error:

undefined local variable or method 'confirmed_at' for #User

Anybody has a clue?

Ok. I solved it. The migration is outdated. Generate new migration with same code but another name.

1.Run command:

rails g migration add_confirmable_to_devise_v1

2.In the migration file:

class AddConfirmableToDeviseV1 < ActiveRecord::Migration
  def change
    change_table(:users) do |t| 
      t.confirmable 
    end
    add_index  :users, :confirmation_token, :unique => true 
  end
end

3.Then

rake db:migrate