Wierd issues when performing selector "selectAll" on UITextField - ios

Question

I am facing the the wierdest bug (ether in my app or in IOS 7.1) ever.
After many hours I managed to create a simple app that demonstrate the problem.
Two UITextField - Dragged and dropped from interface builder and wired to t1, t2.
the ViewController:
#implementation ViewController
#synthesize t1;
#synthesize t2;
#pragma mark - UITextFieldDelegate
-(void)textFieldDidBeginEditing:(UITextField *)iTextField {
NSLog(#"textFieldDidBeginEditing");
[iTextField performSelector:#selector(selectAll:) withObject:iTextField afterDelay:0.0];
}
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
return YES;
}
- (void)viewDidLoad
{
[super viewDidLoad];
t1.delegate = self;
t2.delegate = self;
}
#end
When tapping on t1 and t2 at the same time, both textFields become first responder in an endless loop!
When omitting ether the PerformSelector statement or the textField:shouldChangeCharactersInRange: implementation, problem is gone.
Can someone explain why does it happen?

Answer 1

Edit: Also set the exclusiveTouch property of each UITextField to: YES to prevent them from editing at the same time.
- (void)viewDidLoad
{
[super viewDidLoad];
t1.exclusiveTouch = YES;
t2.exclusiveTouch = YES;
t1.delegate = self;
t2.delegate = self;
}
- (void)textFieldDidBeginEditing:(UITextField *)iTextField
{
[iTextField performSelector:#selector(selectAll:) withObject:nil afterDelay:0.0];
}
Or more simply without using the exclusiveTouch properties:
- (BOOL)textFieldShouldBeginEditing:(UITextField *)iTextField
{
if (iTextField == t1 && t2.isFirstResponder == NO)
{
return YES;
}
else if (iTextField == t2 && t1.isFirstResponder == NO)
{
return YES;
}
return NO;
}

Answer 2

I try to use the selectedTextRange property to instead of selectAll, it makes the endless loop's problem gone.
func textFieldDidBeginEditing(_ textField: UITextField) {
DispatchQueue.main.async {
let begin = textField.beginningOfDocument
let end = textField.endOfDocument
textField.selectedTextRange = textField.textRange(from: begin, to: end)
}
}