rubymotion/sugarcube — pull request #119 by otagi (2014-02-07 19:15:12+00:00)
Title: Fix to avoid a cyclic reference in UIBarButtonItem.

Push this controller on a navigation controller stack:

```ruby
class LeakyController < UIViewController
def viewWillAppear(animated)
super
self.navigationItem.leftBarButtonItem = UIBarButtonItem.done { go_back }
end

def go_back
navigationController.popViewControllerAnimated(true)
end

def dealloc
puts "LeakyController.dealloc"
end
end
```

When `popViewControllerAnimated` is called, `LeakyController` will not be released if `UIBarButtonItem` has a strong ref on the action block.