How to use std::find/std::find_if with a vector of custom class objects?

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I have a class representing a user called Nick and I want to use std::find_if on it, where I want to find if the userlist vector has an object included with the same username I pass in. I did a few attempts by trying to create a new Nick object for the username I want to test and overloading the == operator and then trying to use find/find_if on the object:

    std::vector<Nick> userlist;
    std::string username = "Nicholas";

if (std::find(userlist.begin(), userlist.end(), new Nick(username, false)) != userlist.end())) {
    std::cout << "found";
}

I have overloaded the == operator so comparing Nick == Nick2 should work, but the function returns error C2678: binary '==' : no operator found which takes a left-hand operand of type 'Nick' (or there is no acceptable conversion).

Here is my Nick class for reference:

class Nick {
private:
    Nick() {
        username = interest = email = "";
                    is_op = false;
    };
public:
    std::string username;
    std::string interest;
    std::string email;
    bool is_op;

    Nick(std::string d_username, std::string d_interest, std::string d_email, bool d_is_op) {
        Nick();
        username = d_username;
        interest = d_interest;
        email = d_email;
        is_op = d_is_op;
    };
    Nick(std::string d_username, bool d_is_op) {
        Nick();
        username = d_username;
        is_op = d_is_op;
    };
    friend bool operator== (Nick &n1, Nick &n2) {
        return (n1.username == n2.username);
    };
    friend bool operator!= (Nick &n1, Nick &n2) {
        return !(n1 == n2);
    };
};
stl-algorithm stl c++
7 Answers

This works for me:

Nick.h

#include <string>

class Nick {
private:
    Nick() {
        username = interest = email = "";
        is_op = false;
    };
public:
    std::string username;
    std::string interest;
    std::string email;
    bool is_op;

    Nick(std::string d_username, std::string d_interest, std::string d_email, bool d_is_op) {
        Nick();
        username = d_username;
        interest = d_interest;
        email = d_email;
        is_op = d_is_op;
    };
    Nick(std::string d_username, bool d_is_op) {
        Nick();
        username = d_username;
        is_op = d_is_op;
    };

    bool operator==(const Nick& refNick) const
    {
        if (username != refNick.username)
            return false;
        if (interest != refNick.interest)
            return false;
        if (email != refNick.email)
            return false;
        if (is_op != refNick.is_op)
            return false;
        return true;
    }

    bool operator!=(const Nick& refNick) const
    {
        if (username == refNick.username)
            return true;
        if (interest == refNick.interest)
            return true;
        if (email == refNick.email)
            return true;
        if (is_op == refNick.is_op)
            return true;
        return false;
    }
};

main.cpp

#include <iostream>
#include <string>
#include <vector>
#include "Nick.h"

int main()
{
    std::vector<Nick> userlist;
    std::string username = "Nicholas";    
    Nick Nicholas(username, false);
    Nick John("John", true);        
    userlist.push_back(Nicholas);

    std::vector<Nick>::iterator it;

    it = std::find(userlist.begin(), userlist.end(), Nick("Nicholas", false));
    if(it != userlist.end())
        std::cout << "\n" << Nicholas.username << " was found.";
    else
        std::cout << "\n" << Nicholas.username << " was not found.";

    it = std::find(userlist.begin(), userlist.end(), John);
    if (it != userlist.end())
        std::cout << "\n" << John.username << " was found.";
    else
        std::cout << "\n" << John.username << " was not found.";
}

Result

Nicholas was found.
John was not found.
user_13415230
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