This error is probably due to changes in Xcode since the book was printed. Using recent versions (RubyMotion Starter 4.11 and Xcode 7.3), depending on the example, it is preceded by
- Terminating app due to uncaught exception
- Assertion failure
gives a solution.
My solution is simply adding the following line in app_delegate.rb :
@window.rootViewController = UIViewController.new
Example for Boxey_textfield :
class AppDelegate def application(application, didFinishLaunchingWithOptions:launchOptions) @window = UIWindow.alloc.initWithFrame(UIScreen.mainScreen.bounds) @window.backgroundColor = UIColor.whiteColor @window.makeKeyAndVisible # added : @window.rootViewController = UIViewController.new etc...