UITextField subclass throwing weird exception at becomeFirstResponder - ios

Question

I have character boxes made of my UINavigatableTextField. After each input, responder character should succeed to it's successor. Weirdly, during input of first character, if user enters character 'Q' each time different exception like;
EXC_BAD_ACCESS, or
2012-09-04 14:42:42.600 Kelime Oyunu[6350:707] -[WebScriptObjectPrivate isForShortcutConversion]: unrecognized selector sent to instance 0x21b870
2012-09-04 14:42:42.606 Kelime Oyunu[6350:707] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[WebScriptObjectPrivate isForShortcutConversion]: unrecognized selector sent to instance 0x21b870'
is thrown. My code receiving exception below, the [next becomeFirstResponder] line
- (void) moveToNextCharacter: (MBNavigatableTextField *) character
{
dispatch_async(dispatch_get_current_queue(),
^{
UIControl *next = [character nextField];
if(next == nil)
{
[character endEditing:YES];
}
else if ([next isKindOfClass:[UIButton class]])
{
[next sendActionsForControlEvents: UIControlEventTouchUpInside];
}
else
{
[next becomeFirstResponder];
}
});
}
How can i solve the problem? Thanks in advance.
Edit 1: Found a zombie [next resignFirstResponder] (Thanks to #PhillipMills)
Edit 2: It turns out my problem caused from
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
// Something done here...
// code block of evil zombie summoner
[textField setText:#"Some text"];
// Something else done here
}
Profile->Instruments->Zombies stating that during setText: some object is released (which is previous string i guess).
I am still unable to solve the problem. My goal is updating textField above with new user input (replacementString:).

Answer 1

All messaging to UIKit objects has to be done on the main queue. While that may be the case, this statement:
dispatch_async(dispatch_get_current_queue()
is troublesome since we don't know what queue you get the message on. Change it to:
dispatch_async(dispatch_get_main_queue()
so its absolutely clear.
Also, under this line:
UIControl *next = [character nextField];
add these statements:
NSLog(#"Character CLASS %#", NSStringFromClass[character class]);
NSLog(#"next CLASS %#", NSStringFromClass[next class]);
Make sure these are what you think they should be.
EDIT: Regarding the use of "unsafe_unretained": if a IBOutlet is contained within "self.view" - that is the primary view - then you should be using weak on iOS - so it gets nil'd for you when the view goes away.
Regarding 'shouldChangeCharactersInRange', if you are simply looking at the characters, you return YES. If you change the text itself - by writing to the field/view directly, then return NO. If you modify text and then return YES, you're in essence changing data behind the control's back with who knows what consequences.