How do I limit characters in UITextView ?
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)string {
        NSUInteger newLength = [textField.text length] + [string length] - range.length;
        return (newLength > 25) ? NO : YES;
    }

-(IBAction)checkIfCorrectLength:(id)sender{
    [self textView:myTextView shouldChangeTextInRange: ?? replacementText: ?? ];

}

- (BOOL)isAcceptableTextLength:(NSUInteger)length {
    return length <= 25;
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)string {
    return [self isAcceptableTextLength:textField.text.length + string.length - range.length];
}

-(IBAction)checkIfCorrectLength:(id)sender{
    if (![self isAcceptableTextLength:self.textField.text.length]) {
        // do something to make text shorter
    }
}