app_delegate.rb

# -*- coding: utf-8 -*-
class AppDelegate
  def application(application, didFinishLaunchingWithOptions:launchOptions)
    @window = UIWindow.alloc.initWithFrame(UIScreen.mainScreen.bounds)
    controller = MainViewController.alloc.init
    @window.rootViewController = UINavigationController.alloc.initWithRootViewController(controller)
    @window.makeKeyAndVisible
    true
  end
end

class MainViewController < UIViewController
  def viewDidLoad
    super
    button = UIBarButtonItem.alloc.initWithBarButtonSystemItem(UIBarButtonSystemItemBookmarks, target:self, action:'open_modal')
    self.view.backgroundColor = UIColor.whiteColor
    self.navigationItem.rightBarButtonItem = button
  end

  def open_modal
    modal   = ModalViewController.alloc.init
    nav = UINavigationController.alloc.initWithRootViewController(modal)
    self.presentModalViewController(nav, animated:true)
  end
end

class ModalViewController < UITableViewController
  def viewDidLoad
    super
    @obj = MyObject.new

    ## パターン1: 普通の呼び方 => dealloc は呼ばれる
    # button =  UIBarButtonItem.alloc.initWithBarButtonSystemItem(UIBarButtonSystemItemCancel, target:self, action:'dismiss_modal')
    # self.navigationItem.leftBarButtonItem = button

    ## パターン2: sugarcube + closure => dealloc が呼ばれないっぽい、ウゲー
    # self.navigationItem.leftBarButtonItem =
    #  UIBarButtonItem.cancel { self.dismissViewControllerAnimated(true, completion:nil) }

    ## パターン3: => これも暗黙の self があるせいか、dealloc 呼ばれない
    # self.navigationItem.leftBarButtonItem = UIBarButtonItem.cancel { dismiss_modal }

    ## パターン4: これはもちろん OK
    # btn = UIBarButtonItem.cancel
    # btn.action = 'dismiss_modal'
    # btn.target = self
    # self.navigationItem.leftBarButtonItem = btn

    ## dismissViewControllerAnimated とは関係内文脈でクロージャで self を持つと･･･
    # => これをするのも NG
    # ただし、sugarcube が悪いのかどうなのかまでは検証できておらず
    # self.navigationItem.rightBarButtonItem = UIBarButtonItem.titled('hoge') do
    #  self
    # end

    ## パターン5: weakref
    this = WeakRef.new(self)
    self.navigationItem.leftBarButtonItem =
      UIBarButtonItem.cancel { this.dismissViewControllerAnimated(true, completion:nil) }
  end

  def dismiss_modal
    self.dismissViewControllerAnimated(true, completion:nil)
  end

  def dealloc
    NSLog('dealloc ModalViewController')
    super
  end
end

class MyObject
  def dealloc
    NSLog("dealloc MyObject")
    super
  end
end