We can use the UITextField’s delegate method

- (BOOL)textField: (UITextField *)textField shouldChangeCharactersInRange: (NSRange)range replacementString: (NSString *)string

to set the maximum character length.

This can be done by doing the following:

#define MAX_LENGTH 10

- (BOOL)textField: (UITextField *)textField shouldChangeCharactersInRange: (NSRange)range replacementString: (NSString *)string
{
    if (textField.text.length >= MAX_LENGTH && range.length == 0)
    {
        return NO; 
    }
    else
    {
        return YES;
    }
}