Devise install from existing model/database - ruby-on-rails

Question

I am wondering how can i add devise to an existing database with a different user. Here I already have a customer model define and I want to change to allow devise to work on it.
I have created a new migration and inserted the code has follow
class AddDeviseToCustomer < ActiveRecord::Migration
def change
change_table :customers do |t|
#t.database_authenticatable
t.string :encrypted_password, :null => false, :default => '', :limit => 128
t.confirmable
t.recoverable
t.rememberable
t.trackable
t.token_authenticatable
t.timestamps
end
end
end
According to this it should work. https://github.com/plataformatec/devise/wiki/How-To:-change-an-already-existing-table-to-add-devise-required-columns. But when running rake db:migrate i get the following
undefined method `confirmable' for #<ActiveRecord::ConnectionAdapters::Table:0x9286a28>
I have run the following line
rails g devise:install
Any reason devise won't recognize it, do i need to do something to say customer is a devise??
Thanks in advance

Answer 1

It looks like that documentation is outdated.
Try using devise generator, it will create same migration, with correct parameters, it's ok if its an existing model:
rails g devise customer
it should create AddDeviseToCustomers migration
with something similar to this:
class AddDeviseToCustomers < ActiveRecord::Migration
def self.up
change_table(:customers) do |t|
## Database authenticatable
t.string :email, :null => false, :default => ""
t.string :encrypted_password, :null => false, :default => ""
## Recoverable
t.string :reset_password_token
t.datetime :reset_password_sent_at
## Rememberable
t.datetime :remember_created_at
## Trackable
t.integer :sign_in_count, :default => 0
t.datetime :current_sign_in_at
t.datetime :last_sign_in_at
t.string :current_sign_in_ip
t.string :last_sign_in_ip
## Confirmable
t.string :confirmation_token
t.datetime :confirmed_at
t.datetime :confirmation_sent_at
t.string :unconfirmed_email # Only if using reconfirmable
## Lockable
# t.integer :failed_attempts, :default => 0 # Only if lock strategy is :failed_attempts
# t.string :unlock_token # Only if unlock strategy is :email or :both
# t.datetime :locked_at
## Token authenticatable
# t.string :authentication_token
# Uncomment below if timestamps were not included in your original model.
# t.timestamps
end
def self.down
# By default, we don't want to make any assumption about how to roll back a migration when your
# model already existed. Please edit below which fields you would like to remove in this migration.
raise ActiveRecord::IrreversibleMigration
end
end
note that there is no more t.confirmable