While creating any Login or Registration UI in iOS we ask user to enter their email id. To avoid wrong data entry we can validate entered data by using a simple validation method. Below method will return you a BOOL value. Here it is:-

 -(BOOL)validateEmail: (NSString *) candidate {
    NSString *emailRegex = @"(?:[A-Za-z0-9!#$%\\&'*+/=?\\^_`{|}~-]+(?:\\.[A-Za-z0-9!#$%\\&'*+/=?\\^_`{|}" @"~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\" @"x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[A-Za-z0-9](?:[a-" @"z0-9-]*[A-Za-z0-9])?\\.)+[A-Za-z0-9](?:[A-Za-z0-9-]*[A-Za-z0-9])?|\\[(?:(?:25[0-5" @"]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-" @"9][0-9]?|[A-Za-z0-9-]*[A-Za-z0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21" @"-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])";

    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];

    BOOL result = [emailTest evaluateWithObject:candidate];

    return result;
}

Happy Coding!!!