This was my first time doing regular expressions with objective-c. I did not find much out there on regex email validations for objective-c, so figured I'd post my simple example to help anyone out later.
NSPredicate can do a lot more than just regex on a string too. Please let me know if there are better options.
PHP:
NSString *emailRegEx = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegEx];
//Valid email address
if ([emailTest evaluateWithObject:detail] == YES)
{ ... }
//Invalid email address
else
{ ... }