NSString *str = @"1234";
NSString *str1 = @"1234gfd432";
NSString *ptn = @"^[0-9]*$";
 
NSRange range = [str rangeOfString:ptn options:NSRegularExpressionSearch];
NSRange range1 = [str1 rangeOfString:ptn options:NSRegularExpressionSearch];
 
NSLog(@"%d, %d", range.length, range1.length); // 4, 0을 출력

NSString *str = @"1234";
NSString *str1 = @"asdfb-sdf";
NSString *ptn = @"^[a-zA-Z-\_&]*$";
 
NSRange range = [str rangeOfString:ptn options:NSRegularExpressionSearch];
NSRange range1 = [str1 rangeOfString:ptn options:NSRegularExpressionSearch];
 
NSLog(@"%d, %d", range.length, range1.length); // 0, 9 출력

NSString *str = @"1234@abc";
NSString *str1 = @"leegt__@naver.com";
NSString *ptn =
@"^([a-zA-Z0-9-\_]{3,20})@([a-zA-Z0-9-\_]{3,20}).([a-zA-Z0-9-\_.]{2,20})$";
 
NSRange range = [str rangeOfString:ptn options:NSRegularExpressionSearch];
NSRange range1 = [str1 rangeOfString:ptn options:NSRegularExpressionSearch];
 
NSLog(@"%d, %d", range.length, range1.length); // 0, 17 출력

NSString *str = @"1234";
NSString *str1 = @"02-1234-1234";
NSString *ptn = @"([0-9]{2,3})-([0-9]{3,4})-([0-9]{4})";
 
NSRange range = [str rangeOfString:ptn options:NSRegularExpressionSearch];
NSRange range1 = [str1 rangeOfString:ptn options:NSRegularExpressionSearch];
 
NSLog(@"%d, %d", range.length, range1.length); // 0, 12 출력

NSString *str = @"012-123-1234";
NSString *str1 = @"010-1234-1234";
NSString *ptn = @"(010|011|016|017|018|019)-([0-9]{3,4})-([0-9]{4})";
 
NSRange range = [str rangeOfString:ptn options:NSRegularExpressionSearch];
NSRange range1 = [str1 rangeOfString:ptn options:NSRegularExpressionSearch];
 
NSLog(@"%d, %d", range.length, range1.length); // 0, 12 출력

NSString *email = @"picomax@nate.com";
    NSArray *split = [email componentsSeparatedByString:@"@"];
    NSString *pre = [[split objectAtIndex:0] substringWithRange:NSMakeRange(0, 2)];
    NSString *post = [[split objectAtIndex:0] substringWithRange:NSMakeRange(2, [[split objectAtIndex:0] length]-2)];
    
    NSString *template = @"*";
    NSError *error   = nil;
    NSRegularExpression *regexp =
    [NSRegularExpression regularExpressionWithPattern:@"[a-zA-Z0-9-_]"
                                              options:0
                                                error:&error];
    NSString *replaced =
    [regexp stringByReplacingMatchesInString:post
                                     options:0
                                       range:NSMakeRange(0,post.length)
                                withTemplate:template];
    
    NSString *result = ([split count]>1) ? [NSString stringWithFormat:@"%@%@@%@", pre, replaced, [split objectAtIndex:1]] : [NSString stringWithFormat:@"%@%@@%@", pre, replaced, @"nate.com"];