我有一个代表用户的类，名为Nick我想用std::find_if在它上面，我想在其中查找用户列表向量是否包含与我传入的相同用户名包含的对象。我做了一些尝试，尝试创建一个新的Nick我想测试并重载的用户名对象== operator然后尝试使用find/find_if在物体上：
std::vector<Nick> userlist;
std::string username = "Nicholas";
if (std::find(userlist.begin(), userlist.end(), new Nick(username, false)) != userlist.end())) {
std::cout << "found";
}
我已经超载了== operator所以比较 Nick == Nick2 应该可以，但函数会返回error C2678: binary '==' : no operator found which takes a left-hand operand of type 'Nick' (or there is no acceptable conversion).
这是我的 Nick 类供参考：
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);
};
};
如果您使用 C++0X，您可以使用简单的 lambda 表达式
std::string username = "Nicholas";
std::find_if(userlist.begin(), userlist.end(), [username](Nick const& n){
return n.username == username;
})
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