验证邮箱的合法性（此方法比较准确)

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.title=@"验证邮箱的合法性";
    
    NSString *email=@"618712810@.qq.com";
    NSLog(@"---%i--",[self validateEmail:email]);
    
    
}
//通过区分字符串
-(BOOL)validateEmail:(NSString*)email
{
    if((0 != [email rangeOfString:@"@"].length) &&
       (0 != [email rangeOfString:@"."].length))
    {
        NSCharacterSet* tmpInvalidCharSet = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
        NSMutableCharacterSet* tmpInvalidMutableCharSet = [tmpInvalidCharSet mutableCopy];
        [tmpInvalidMutableCharSet removeCharactersInString:@"_-"];
        
        /*
         *使用compare option 来设定比较规则，如
         *NSCaseInsensitiveSearch是不区分大小写
         *NSLiteralSearch 进行完全比较,区分大小写
         *NSNumericSearch 只比较定符串的个数，而不比较字符串的字面值
         */
        NSRange range1 = [email rangeOfString:@"@"
                                      options:NSCaseInsensitiveSearch];
        
        //取得用户名部分
        NSString* userNameString = [email substringToIndex:range1.location];
        NSArray* userNameArray   = [userNameString componentsSeparatedByString:@"."];
        
        for(NSString* string in userNameArray)
        {
            NSRange rangeOfInavlidChars = [string rangeOfCharacterFromSet: tmpInvalidMutableCharSet];
            if(rangeOfInavlidChars.length != 0 || [string isEqualToString:@""])
                return NO;
        }
        
        //取得域名部分
        NSString *domainString = [email substringFromIndex:range1.location+1];
        NSArray *domainArray   = [domainString componentsSeparatedByString:@"."];
        
        for(NSString *string in domainArray)
        {
            NSRange rangeOfInavlidChars=[string rangeOfCharacterFromSet:tmpInvalidMutableCharSet];
            if(rangeOfInavlidChars.length !=0 || [string isEqualToString:@""])
                return NO;
        }
        
        return YES;
    }
    else {
        return NO;
    }
}