在std :: set中找到对象时出错

Question

I am trying to find an object inside the set using the find() method. However, I am unable to do that it seems I am sending a wrong key. What would be right way to do it?

#include <iostream>
#include <set>
#include <utility>

struct Class {
  std::pair<int,int> data;
  int val = 0;
  int id = 0; ///ID for the object

};

struct CompClass {
      bool operator() (const Class& lhs, const Class& rhs) const
  {
    if (lhs.data.first == rhs.data.first) return lhs.data.second < rhs.data.second;

    return lhs.data.first<rhs.data.first;
    }
    };

int main ()
{

  Class c1,c2,c3,c4;


  c1.val = 92;c1.id = 2; c1.data = std::make_pair(92,2);
  c2.val = 94;c2.id = 3; c2.data = std::make_pair(94,3);
  c3.val = 92;c3.id = 1; c3.data = std::make_pair(10,1);

  std::set<Class,CompClass> fifth;                 // class as Compare

    fifth.insert(c1);fifth.insert(c2);fifth.insert(c3);

    for (auto x: fifth) {std::cout << x.id << "  " << x.val << std::endl;} 

    if (fifth.find(  std::make_pair(92,2)  ) != fifth.end() ) {std::cout << "Got it";} //Error

  return 0;
}

Answer 1

std::set<T>::find takes an argument of type T in C++11. You need to provide a Class object, not a std::pair :

if (fifth.find(  Class{92,2,0,0}  ) != fifth.end() ) {std::cout << "Got it";}