Rails%203%20In%20Action

276 CHAPTER 10 Tracking state
def make_default
@state = State.find(params[:id])
@state.default!
flash[:notice] = "#{@state.name} is now the default state."
redirect_to admin_states_path
end
Rather than putting the logic to change the selected state to the new default inside
the controller, you place it in the model. To trigger a state to become the new default
state, you call the default! method on it. It’s best practice to put code that performs
functionality like this inside the model.
This default! method can be defined in the State model, as shown in the following
listing.
def default!
current_default_state = State.find_by_default(true)
end
Listing 10.26 app/controllers/admin/states_controller.rb
Listing 10.27 app/models/state.rb
self.default = true
self.save!
if current_default_state
current_default_state.default = false
current_default_state.save!
end
The find_by_default B method here is a dynamic finder method from Active
Record. The find_by_default will either return the State object for the default
state, or nil. If it doesn’t return nil C then you change its default state to false
and save the record.
When you run your feature again with bin/cucumber features/creating_states
.feature, you see that the find_by_default method isn’t defined:
And I follow "Make default" for the "New" state
undefined method `find_by_default' for State...
This dynamic method doesn’t exist because you haven’t yet defined the default column
on your states table. If you had this column then Rails would have already
defined the find_by_default method for you. To do this, you generate a migration
that will add this column using the following command:
rails g migration add_default_to_states default:boolean
B Dynamic finder
C Change default state
Don’t run this migration just yet. With the default column being a boolean field, it’s
going to need to know what its default value should be: either true or false. To set a