Rails%203%20In%20Action

112 CHAPTER 5 Nested resources
The solution is the second value for this option:
has_many :tickets, :dependent => :delete_all
This simply deletes all the tickets using a SQL delete, like this:
DELETE FROM tickets WHERE project_id = :project_id
This operation is quick and is exceptionally useful if you have a large number of tickets
that don’t have callbacks. If you do have callbacks on Ticket for a destroy operation,
then you should use the first option, :dependent => :destroy.
Finally, if you just want to disassociate tickets from a project and unset the
project_id field, you can use this option:
has_many :tickets, :dependent => :nullify
When a project is deleted with this type of :dependent option defined, it will execute
an SQL query such as this:
UPDATE tickets SET project_id = NULL WHERE project_id = :project_id
Rather than deleting the tickets, this option keeps them around, but their project_id
fields are unset.
Using this option would be helpful, for example, if you were building a tasktracking
application and instead of projects and tickets you had users and tasks. If you
delete a user, you may want to reassign rather than delete the tasks associated with that
user, in which case you’d use the :dependent => :nullify option instead.
In your projects and tickets scenario, though, you use :dependent => :destroy if
you have callbacks to run on tickets when they’re destroyed or :dependent =>
:delete_all if you have no callbacks on tickets.
This was a little bit of a detour for the work you’re doing now, but it’s a nice thing
to know if you ever need to delete an associated object when the original object is
deleted.
Let’s look at how to edit the tickets in your application.
5.3 Editing tickets
You want users to be able to edit tickets, the updating part of this CRUD interface. This
section covers creating the edit and update actions for the TicketsController.
The next feature you’re going to implement is the ability to edit tickets. This functionality
follows a thread similar to the projects edit feature where you follow an Edit
link in the show template. With that in mind, you can write this feature using the code
in the following listing and put it in a file at features/editing_tickets.feature.
Listing 5.12 features/editing_tickets.feature
Feature: Editing tickets
In order to alter ticket information
As a user
I want a form to edit the tickets