Declarative Authorization - Catch "Authorization::NotAuthorized" Exception - ruby-on-rails

Question

I'm currently using Declarative Authorization on my application, and trying to catch Exceptions from type Authorization::NotAuthorized.
I have an Entity that has a category. Depending on the role a user can create a new category when creating this entity. At my :before_validation callback I assign the category and want to be able to catch the authorization exception in case he doesn't have permission.
I could check it's role and make a conditional instruction, but then would have to write all the roles.
Exception is being thrown, but I'm not able to catch it, at the "new" instruction.
Code follows:
# Model
before_validation :set_category
def category_name
#category_name ||= category.name unless category.nil?
#category_name
end
def category_name=(name)
name.strip!
name.downcase!
#category_name = name
end
def set_category
if #category_name and not company.blank?
lookup_category = company.categories.not_deleted.find_by_name(#category_name)
begin
category = lookup_category.blank? ? company.categories.new(:name => #category_name) : lookup_category
rescue Authorization::NotAuthorized
errors.add(:category, I18n.t('activerecord.errors.messages.exclusion'))
end
end
end
# Controller
def create
#ticket = current_user.created_tickets.new(params[:ticket])
if #ticket.save # Line 88
...
Exception stack trace:
Authorization::NotAuthorized (No matching rules found for create for #<User id: 36,..."> (roles [:Requester], privileges [:create], context :categories).):
/Library/Ruby/Gems/1.8/gems/declarative_authorization-0.4.1/lib/declarative_authorization/authorization.rb:168:in `permit!'
/Library/Ruby/Gems/1.8/gems/declarative_authorization-0.4.1/lib/declarative_authorization/in_model.rb:131:in `using_access_control'
/Library/Ruby/Gems/1.8/gems/after_commit-1.0.7/lib/after_commit/connection_adapters.rb:12:in `transaction'
/Library/Ruby/Gems/1.8/gems/after_commit-1.0.7/lib/after_commit/connection_adapters.rb:12:in `transaction'
app/controllers/tickets_controller.rb:88:in `create'
Debugger goes inside the block:
# Debugger
lookup_category = company.categories.not_deleted.find_by_name(#category_name)
(rdb:3) list
[275, 284] in /Users/Pedro/projects/trunk/app/models/ticket.rb
275
276 def set_category
277 if #category_name and not self.company.blank?
278 begin
279 debugger
=> 280 lookup_category = company.categories.not_deleted.find_by_name(#category_name)
281 self.category = lookup_category.blank? ? company.categories.new(:name => #category_name) : lookup_category
282 rescue Authorization::NotAuthorized
283 self.errors.add(:category, I18n.t('activerecord.errors.messages.exclusion'))
284 end
(rdb:3) n
/Users/Pedro/projects/trunk/app/models/ticket.rb:281
self.category = lookup_category.blank? ? company.categories.new(:name => #category_name) : lookup_category
(rdb:3) list
[276, 285] in /Users/Pedro/projects/trunk/app/models/ticket.rb
276 def set_category
277 if #category_name and not self.company.blank?
278 begin
279 debugger
280 lookup_category = company.categories.not_deleted.find_by_name(#category_name)
=> 281 self.category = lookup_category.blank? ? company.categories.new(:name => #category_name) : lookup_category
282 rescue Authorization::NotAuthorized
283 self.errors.add(:category, I18n.t('activerecord.errors.messages.exclusion'))
284 end
285 end
(rdb:3) n
/Users/Pedro/.gem/ruby/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb:94
break result if terminator.call(result, object)
(rdb:3) list
[89, 98] in /Users/Pedro/.gem/ruby/1.8/gems/activesupport-2.3.8/lib/active_support/callbacks.rb
89 unless block_given?
90 send(enumerator) { |callback| callback.call(object) }
91 else
92 send(enumerator) do |callback|
93 result = callback.call(object)
=> 94 break result if terminator.call(result, object)
95 end
96 end
97 end
98
(rdb:3)

Answer 1

I'd say that it's breaking outside the begin ... rescue block and therefore not caught by the rescue. Try to do the same rescue on line 88 of your controller.
If you want to handle this in the validation process, maybe try to do a test on the roles or permissions of the user before creating your object instead of catching the exception that will only be thrown on creation.

Answer 2

It's not possible to catch the exception on a before callback. The best way I found to do this kind of validation is:
# Model code
begin
User.with_permissions_to :create, :categories # Raises exception if not permitted
... do whatever you want
rescue
... do whatever you want
end
Thanks for all the help