Question

I recently inherited maintenance of a relatively small iOS application. The app was created by external contractors with very little guidance and oversight. Needless to say it needs “a little” cleaning – I am evaluating whether to redo the entire thing or not.

One thing that got me stumped is a crash in the app whereby the debugger shows “Applications are expected to have a root view controller at the end of application launch”. In the module where this occurs, I researched all UIViews to make sure they are created with a parent (addSubView sets the root view controller, right?) – this seems all prim and proper.

Being rather new to XCode, I am not familiar with facilities that help me figure out what might be going on here. E.g., how can I quickly see/investigate the status of all UIViews created by a module? How can I ‘watch’ a variable just to be alerted when it changes? And in general, is there a best strategy to use to tackle issues like the one I described above?

Sorry to stay a bit vague but I don’t think that publishing a bunch of ugly code helps you to understand the problem better 🙂

Answer 1

That particular problem happens when the application’s UIWindow doesn’t have a value for its rootViewController property by the time it finishes launching. Take a look in your application delegate file – usually, the root view controller is set on the window there.

With regards to your more general questions: there are a variety of ways to inspect the state of your program as it runs. A very basic way to dump some info is to use an NSLog statement – you can print out messages to the console in much the same way as a C printf would. You can also set breakpoints in your application and use the debugger to inspect different variables – take a look at the lldb documentation for more info.