Troubles with std::set.insert c-CodePudding

I have a set of a custom class and when I'm trying to insert an object of that class, the terminal gives me an error:

#ifndef EMPLOYEE_HH
#define EMPLOYEE_HH

#include <string>
#include <iostream>
#include <set>
#include <iterator>
using namespace std ;

class Employee {

public:
  // Constructor
  Employee(const char* name, double salary) : _name(name), _salary(salary) {}

  // Accessors
  const char* name() const { return _name.c_str() ; }
  double salary() const { return _salary ; }

  // Print functions
  void businessCard(ostream& os = cout) const {
    os << "    ------------------   " << endl
       << "   | ACME Corporation |  " << endl 
       << "    ------------------   " << endl
       << "   " << name() << endl ;
  }
  
private:

  string _name ;
  double _salary ;
} ;

class Manager : public Employee{
  public:
  
  Manager(const char* name, double salary) : Employee(name, salary) {};

  void addSubordinate(Employee& empl){
    _subs.insert(empl);
  }

  const set<Employee*>& listOfSubordinates() const{
    return _subs;  
  }

  void businessCard() const{
    Employee::businessCard();
    
    set <Employee*>::iterator it=_subs.begin();
    cout <<"Managed employees: " <<endl;
    while(it!=_subs.end()){
      cout <<*it   <<endl;
    }
  }
  private:
  set <Employee*> _subs;
};

#endif

The addSubordinate() routine:

void addSubordinate(Employee& empl){
        _subs.insert(empl);
      }

returns this error:

no instance of overloaded function "std::set<_Key, _Compare, _Alloc>::insert [with _Key=Employee *, _Compare=std::less<Employee *>, _Alloc=std::allocator<Employee *>]" matches the argument list

I have tried to overload the operator < as other people suggested in response to similar questions, but that doesn't seem to solve the issue.

CodePudding user response：

You need to define the < operator in the Employee class. The items in a set are always sorted and since you don't have a comparator it won't let you insert an instance of that class. Try something like this:

bool operator<(const Employee& emp){
    return salary() < emp.salary();
}

CodePudding user response：

Your set accepts a pointer to an Employee, but you are trying to insert the object itself.

What you can do is

void addSubordinate(Employee& empl){
    _subs.insert(&empl); // This will store the address to the object
  }

or accept a pointer itself

void addSubordinate(Employee* empl){
    _subs.insert(empl);
  }