textfield只允许输入数字

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
NSString *text = [self.bankNumTextFeild text];
        
        NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789\b"];
        string = [string stringByReplacingOccurrencesOfString:@" " withString:@""];
        
        if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {
            return NO;
        }

return YES;
}