How to limit text input and count characters? - objective-c

Question

I have a text field and I want to limit the text that can be entered to 160 chars. Besides I need a counter to get the current text length.
I solved it using a NSTimer:
[NSTimer scheduledTimerWithTimeInterval:0.5 target:self
selector:#selector(countText)
userInfo:nil
repeats:YES];
And I display the length this way:
-(void)countText{
countLabel.text = [NSString stringWithFormat:#"%i",
_textEditor.text.length];
}
This is not the best counter solution, because it depends on time and not on keyUp event. Is there a way to catch such an event and triggere a method?
The othere thing is, is it possible to block/limit text input, e.g. by providing a max length parameter on the text field?

Answer 1

This is (or should be) the correct version of the delegate method:
- (BOOL)textView:(UITextView *)aTextView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {
// "Length of existing text" - "Length of replaced text" + "Length of replacement text"
NSInteger newTextLength = [aTextView.text length] - range.length + [text length];
if (newTextLength > 160) {
// don't allow change
return NO;
}
countLabel.text = [NSString stringWithFormat:#"%i", newTextLength];
return YES;
}

Answer 2

implement some of UITextFieldDelegate protocol methods
_textEditor.delegate = self;
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
int len = [textField.text length];
if( len + string.length > max || ){ return NO;}
else{countLabel.text = [NSString stringWithFormat:#"%i", len];
return YES;}
}

Answer 3

you can use the delegate method
- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
if(textField.length < max){
return NO;
}else return YES;
}
and set the max length and return NO.

Answer 4

Use following code to limit the characters in UITextField, following code accepts 25 characters in UITextField.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSUInteger newLength = [textField.text length] + [string length] - range.length;
return (newLength > 25) ? NO : YES;
}