Question

I want to make a user login form and it needs to use emails not just usernames. Is there any way i can make a alert pop up if it is not an email? btw All of this is in xcode.

Answer 1

There is a way using NSPredicate and regular expression:

- (BOOL)validateEmail:(NSString *)emailStr {
    NSString *emailRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
    return [emailTest evaluateWithObject:emailStr];
}

Then, you can display an alert if email address is wrong:

- (void)checkEmailAndDisplayAlert {
    if(![self validateEmail:[aTextField text]]) {
        // user entered invalid email address
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Enter a valid email address." delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
        [alert show];
        [alert release];
    } else {
        // user entered valid email address
    }
}