How to find a set of characters in a string

Question

I am working on a project and I am facing a problem. I need to find a set of characters in a string like if user enters his/her email then i have to check whether the email is correct or not. I am finding it to use the string class find function but i haven't succeeded. I can use the loop to find the last character but I and looking for a simplest method to work for it. Example: email@gmail.com I want to get .com as the last characters of string.

Here is the code of mine:

string checkEmail(const char* const prompt) {
    string str;
    bool check = true;
    do {
        cout << prompt << " : ";
        cin >> str;
        if (str.find_last_of(".com")) // here is the error, I think
            check = false;
    } while (check);
    return str;
}

Answer 1

You can use std::string::substr to first get the last 4 characters as an std::string , then you can compare it with ".com":

std::string email = "example@mail.com";
std::string ext = email.substr(email.length() - 4, 4);
bool check = ext == ".com";

Answer 2

To check if it was not found:

if (str.find_last_of(".com")==std::string::npos){
    check = false;
}

---

To check if it was found:

if (str.find_last_of(".com")!=std::string::npos){
    check = false;
}