Question

I am trying to access the UITextView delegates and have a problem

I have a UIViewController with the UITextViewDelegate protocol and a Nib containing the textView.

If I set the delegate inside viewDidLoad like “textView.delegate = self” and I touch the textView, the app crashes without logging errors.
If I start editing the textView with code like “[textView becomeFirstResponder]” all delegates get called.

When I set the delegate in the Nib creating a connection between the textView and the File’s owner and deleting “textView.delegate = self” also no delegates get called.

What am I doing wrong here?

Regards,

Elias

Answer 1

It’s not easy to help you without more description, posted code or a xib file.

You say application crashes without any logging errors – well, do you mean that there’s no output in console’s window ? That is normal, for an app that has crashed.

Anyway, you should be able to get the stack-trace to figure out where approximately the application has crashed. Open the debugger (⇧⌘Y), and see the position. That should give you an idea of what went wrong.

Here you can see an example of such debugger session (after EXC_BAD_CRASH):

First two lines doesn’t give us much information, but later on we can see that application has crashed while loading user interface from a NIB file. Well, usually the only code that executes during such load are awakeFromNib methods – it’s up to you to find a problem along those lines.

Often top of code’s execution doesn’t make any sense – for example you might see your ViewController method somewhere, but the top few function calls (those where the code crashed) are located in methods/classes which you never call in your code. In most cases that is a sign of wrong memory de-/allocation. What might happened is that you forgot to retain some of your objects, it has already been released, but you are still keeping reference (a pointer) to its memory. Because that memory has been in fact freed, another object took its place later on, usually some Apple’s internal object you’ve never heard about. Later on your code tries to message your poor object but it sends a message to something completely different. BUMMER! That’s how you get those crashes and strange stack traces.

To fix the kind of problem I’ve just described you can use Instruments and its Zombies instrument. Unfortunately you can’t start Zombies from within Xcode, you need to start Instruments standalone, then choose the Zombies under iPhone Simulator/Memory, then Choose Target from the toolbar, you should see your application in there, or be able to navigate to it on filesystem.

What Zombies instrument does is that it never really frees memory after objects are deallocated. Instead, it will mutate those objects into NSZombie class. That class intercepts all calls to itself, and informs you when some code is trying to send a message to it.

This is how such Instruments session looks like (this is the same crash as seen in debugger above):

In the table you can see that we’re trying to message UIScrollView that has already been deallocated. You can as well see the whole history of retain/release calls to this particular object. That way you can find a missing retain or wrong release/autorelease.

Remember – Zombies Instruments can only be used with Simulator, because there’s not enough memory on the real device to keep all those memory blocks.

Hopefully I could help you with further analysis of your problem.