ObjectiveC判断邮箱地址合法性

- (BOOL)validateEmail:(NSString *) candidate {
    NSString *emailRegex =
    @"(?:[a-z0-9!#$%\&'*+/=?\^_`{|}~-]+(?:\.[a-z0-9!#$%\&'*+/=?\^_`{|}"
    @"~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\"
    @"x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-"
    @"z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5"
    @"]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-"
    @"9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21"
    @"-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])";
    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES[c] %@", emailRegex];

    return [emailTest evaluateWithObject:candidate];
}