Rails%203%20In%20Action

166 CHAPTER 8 More authorization
Underneath the there is a project step in the Background for this feature is a
new step B. It’s responsible for giving the specified user access to the specified project,
but not just any permission: permission to view the project. This step is currently
undefined, so when you run bin/cucumber features/viewing_projects.feature,
you get the step definition for it:
Given /^"([^"]*)" can view the "([^"]*)" project$/ do |arg1, arg2|
pending # express the regexp above with the code you wish you had
end
To implement this step, you use the not-yet-existent Permission model, which stores
the permissions in the database. This model needs a related table called permissions,
which contains three fields.
The first field is the action field, which keeps track of the type of permission a
user has on particular objects. The objects can be of different types, so you must create
two fields to track the association to the object: thing_type and thing_id. This
kind of association is called a polymorphic association, poly meaning “many” and morphic
meaning “forms,” which is fitting. You’ll see more on these in a little while.
One more field you add to this permissions table is a user_id column linking that
Permission to a User.
With all of that in mind, you can define this step in a new file at features/
step_definitions/permission_steps.rb, as shown in the following listing.
Listing 8.2 features/step_definitions/permission_steps.rb
Given /^"([^"]*)" can view the "([^"]*)" project$/ do |user, project|
Permission.create!(:user => User.find_by_email!(user),
:thing => Project.find_by_name!(project),
:action => "view")
end
In listing 8.2, you create a new Permission record with the action defined as view
linking the project and user passed in. This record defines the users who can access
the project. When you run this feature, you get an error because the Permission class
is not yet defined:
And "user@ticketee.com" can view the "TextMate 2" project
uninitialized constant Permission (NameError)
Define it now by generating the model using the following command, typed all on
one line:
rails generate model permission user_id:integer thing_id:integer
thing_type:string action:string
With this model and its related migration, you can run rake db:migrate and rake
db:test:prepare to set up the development and test databases. When you run your
feature again, you get this error message:
And "user@ticketee.com" can view the "TextMate 2" project
unknown attribute: user (ActiveRecord::UnknownAttributeError)