ios 开发：布局之 tab bar, navigator

这两个都跟 html中的很像。 

html 中的 tab 会切换两个DIV， 而 ios 中tab bar (UITabBarControllers) 也是一样：会切换多个controller  对应的view.

# in your app_delegate:
class AppDelegate
  def application(application, didFinishLaunchingWithOptions:launchOptions)
      @window = UIWindow.alloc.initWithFrame(UIScreen.mainScreen.bounds)
      @window.makeKeyAndVisible

      controller = TapController.alloc.initWithNibName(nil, bundle: nil)
      nav_controller = UINavigationController.alloc.initWithRootViewController controller

      other_controller = UIViewController.alloc.initWithNibName nil, bundle: nil     
      other_controller.title = 'Other'
      other_controller.view.backgroundColor = UIColor.purpleColor

      tab_controller = UITabBarController.alloc.initWithNibName nil, bundle: nil
      tab_controller.viewControllers = [nav_controller, other_controller]
      @window.rootViewController = tab_controller
      true
  end     
end

navigator (UINavigationControllers) 则是页面最上方的 “前进”， “后退”一样的东东。

# in your view controller
def viewDidLoad
        right_button = UIBarButtonItem.alloc.initWithTitle 'Push',
            style: UIBarButtonItemStyleBordered, target: self,
            action: 'push'
        self.navigationItem.rightBarButtonItem = right_button
end