```ruby
class DeviseInvitableAddTo<%= table_name.camelize %> < ActiveRecord::Migration
  def up
    change_table :<%= table_name %> do |t|
      t.string     :invitation_token
      t.datetime   :invitation_created_at
      t.datetime   :invitation_sent_at
      t.datetime   :invitation_accepted_at
      t.integer    :invitation_limit
      t.references :invited_by, :polymorphic => true
      t.integer    :invitations_count, default: 0
      t.index      :invitations_count
      t.index      :invitation_token, :unique => true # for invitable
      t.index      :invited_by_id
    end

    # And allow null encrypted_password and password_salt:
    change_column_null :<%= table_name %>, :encrypted_password, true
<% if class_name.constantize.columns_hash['password_salt'] -%>
    change_column_null :<%= table_name %>, :password_salt,      true
<% end -%>
  end

  def down
    change_table :<%= table_name %> do |t|
      t.remove_references :invited_by, :polymorphic => true
      t.remove :invitation_limit, :invitation_sent_at, :invitation_accepted_at, :invitation_token, :invitation_created_at
    end
  end
end
```

Remove invitations_count on inviteable drop
user
```ruby
class DeviseInvitableAddTo<%= table_name.camelize %> < ActiveRecord::Migration
  def up
    change_table :<%= table_name %> do |t|
      t.string     :invitation_token
      t.datetime   :invitation_created_at
      t.datetime   :invitation_sent_at
      t.datetime   :invitation_accepted_at
      t.integer    :invitation_limit
      t.references :invited_by, :polymorphic => true
      t.integer    :invitations_count, default: 0
      t.index      :invitations_count
      t.index      :invitation_token, :unique => true # for invitable
      t.index      :invited_by_id
    end

    # And allow null encrypted_password and password_salt:
    change_column_null :<%= table_name %>, :encrypted_password, true
<% if class_name.constantize.columns_hash['password_salt'] -%>
    change_column_null :<%= table_name %>, :password_salt,      true
<% end -%>
  end

  def down
    change_table :<%= table_name %> do |t|
      t.remove_references :invited_by, :polymorphic => true
      t.remove :invitations_count, :invitation_limit, :invitation_sent_at, :invitation_accepted_at, :invitation_token, :invitation_created_at
    end
  end
end
```
assistant