In CanCanCan version 13.0 and above, a breaking change was introduced to speed up CanCanCan applications with lots of rules. Unfortunately, it breaks DraperDecorator. DraperDecorator suggests that you should use decorates_assigned instead, but this is not feasable or worthwhile for most people since it requires changing every reference in the views from '@object' to simply 'object'. Additionally, if you need to reference can? in a view, it still breaks. So something like this code in your view doesn't work for a decorated object:
This gem provides a simple one line change to restore sanity - simply include the gem and add a line to your ability class.
Here are some references:
- CanCanCan speedup
- breaking change discussion
- more change discussion
- [Official DraperDecorator recommendation][https://github.com/drapergem/draper#when-to-decorate-objects]
Typical error caused by this breaking change is something along the lines of "Not authorized to :read Foo decorator", where Foo was the class that got decorated. Here's the exact error I stumbled across:
(#<Foo:0x007fcdc917a950>).authorization_error(#<CanCan::AccessDenied: You are not authorized to show foo decorator.>
Add this line to your application's Gemfile:
gem 'draper-cancancan'And then execute:
$ bundle
Or install it yourself as:
$ gem install draper-cancancan
and that's it.
In your CanCan ability class, prepend Draper::CanCanCan like this:
class Ability
include CanCan::Ability
prepend Draper::CanCanCan
...
That's it.
After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.
Bug reports and pull requests are welcome on GitHub at https://github.com/GoodMeasuresLLC/draper-cancancan. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.
The gem is available as open source under the terms of the MIT License.