Prevent consecutive "." in email address in iPhone application

Question

Is there any way to prevent consecutive "." in email address using NSPredicate? I can check it other way that whether current and previous input is ".". But I already use NSPredicate. Thus, if I just have to include some condition in that only then I prefer this. My code :

NSString * email = self.emailTextField.text;
NSString *emailRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
NSPredicate *emailValidation =[NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
BOOL isValidEmail = [emailValidation evaluateWithObject:email];

Thank you.

Answer 1

You can try modifying the middle part of your expression to use (?!\\.) negative lookahead for matches of the dot . character, like this:

[A-Z0-9a-z._%+-]+@([A-Za-z0-9-]|\\.(?!\\.))+\\.[A-Za-z]{2,4}

The \\.(?!\\.) anywhere in an expression says "match a single dot only when the symbol that follows is not a dot". The symbol that follows does not get consumed in the process of checking the lookahead. If you want to prevent dots in the e-mail's initial part as well, modify the part before @ in the same way as the middle part:

([A-Z0-9a-z_%+-]|\\.(?!\\.))+@([A-Za-z0-9-]|\\.(?!\\.))+\\.[A-Za-z]{2,4}