Regular expression for Email validation in iPhone app.

-(BOOL)validateEmail:(NSString*)email{

if( (0 != [email rangeOfString:@"@"].length) &&  (0 != [email rangeOfString:@"."].length) )

{

NSMutableCharacterSet *invalidCharSet = [[[[NSCharacterSet alphanumericCharacterSet] invertedSet]mutableCopy]autorelease];

[invalidCharSet removeCharactersInString:@"_-"];

NSRange range1 = [email rangeOfString:@"@" options:NSCaseInsensitiveSearch];

// If username part contains any character other than "."  "_" "-"

NSString *usernamePart = [email substringToIndex:range1.location];

NSArray *stringsArray1 = [usernamePart componentsSeparatedByString:@"."];

for (NSString *string in stringsArray1) {

NSRange rangeOfInavlidChars=[string rangeOfCharacterFromSet: invalidCharSet];

if(rangeOfInavlidChars.length !=0 || [string isEqualToString:@""])

return NO;

}

NSString *domainPart = [email substringFromIndex:range1.location+1];

NSArray *stringsArray2 = [domainPart componentsSeparatedByString:@"."];

for (NSString *string in stringsArray2) {

NSRange rangeOfInavlidChars=[string rangeOfCharacterFromSet:invalidCharSet];

if(rangeOfInavlidChars.length !=0 || [string isEqualToString:@""])

return NO;

}

return YES;

}

else // no '@' or '.' present

return NO;

}