UITextField限制输入长度

#pragma mark - textField
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
NSInteger section=textField.tag/1000;
NSInteger row=textField.tag%1000;
if (section==0 && (row==0 || row==1)){

//限制长度
NSString *toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string];
if ([toBeString length] > kMaxCharacters){
return NO;
}

//限制字母
NSCharacterSet *set = [[NSCharacterSet characterSetWithCharactersInString:kAllCharacters] invertedSet];
NSString *upperStr = [string uppercaseString];
NSString *filted = [[upperStr componentsSeparatedByCharactersInSet:set] componentsJoinedByString:@""];
NSUInteger len = [toBeString length];
BOOL bReturn = len<=kMaxCharacters && [upperStr isEqualToString:filted];
return bReturn;

}
}