Rails%203%20In%20Action

Changing a ticket’s state
You’re now going to render this partial underneath the “Created by” line on app/
views/tickets/show.html.erb using the following line:
You’re using the short form of rendering a partial here once again, and you conditionally
render it if the ticket has a state. If you don’t have the if at the end and the
state is nil, this will raise an exception because it will try to determine the model
name of nil.
To get this state method for your Ticket, you should add the association method
to the model. This method should go directly above the belongs_to :user line in
app/models/ticket.rb:
belongs_to :state
If you run the feature again it will fail because there’s nothing shown in the #ticket
.state element:
And I should see "Open" within "#ticket .state"
is not true. (Test::Unit::AssertionFailedError)
This is because you’re updating the state on the Comment object you’re creating, not
the associated Ticket object! You’re trying to get the new state to display on the ticket
object so that the users of the application can change the state of a ticket when they
add a comment to it. For this to work, you need to define a callback in your Comment
model.
10.2.3 Callbacks
When a user selects a state from the drop-down box attached to the comment form on
a ticket’s page, you want that ticket’s state to be updated with what that user picked.
To do this you can use a callback to set the ticket’s status when you change it
through the comment form. A callback is a method that’s called either before or after
a certain event. For models, there are before-and-after callbacks for the following
events (where * can be substituted for either before or after):
� Validation (*_validation)
� Creating (*_create)
� Updating (*_update)
� Saving (*_save)
� Destruction (*_destroy)
You’re able to trigger a specific piece of code or method to run before or after any of
these events. The Saving item in the list refers to when a record is saved to the database,
which occurs when a record is created or updated. For your Comment model you want
to define a callback that occurs after a record has been created, and for this you use the
after_create method at the top of your Comment model, as well as a ticket association,
transforming this model into the code shown in the following listing.
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