Multimap problem

[mighty asker]

Hello. I get "error C2664: 'bool NameCompare::operator ()(Product &,Product &)' : cannot convert argument 1 from 'const std::basic_string<char,std::char_traits<char>,std::allocator<char>>' to 'Product &'" when trying to compile this.

#include<iostream>
#include<string>
#include<sstream>
#include<algorithm>
#include<map>
using namespace std;
class Product
{
public:
	Product(string name, double price, string producer);
	~Product();
	double returnprice() const
	{
		return this->price;
	} 
	string returnproducer() const
	{
		return this->producer;
	} 
	string returnname()const
	{
		return this->name;
	}
	

private:
	string name;
	double price;
	string producer;

};
Product::Product(string name, double price, string producer) : name(name), price(price), producer(producer)
{
}
Product::~Product()
{
}
struct NameCompare
{
	bool operator () ( Product &one, Product &two)
	{
		return one.returnname()<two.returnname();
	}
};
int main()
{
	multimap<string, Product, NameCompare>shop_name;
	Product temp = Product("abv", 3.3, "qwerty");
	shop_name.insert(pair<string, Product>("abv", temp));
}

[Ispil]

A multimap's compare operator compares keys, not values. Your multimap uses strings as keys and Product objects as values, while your compare operator expects Product objects as keys.

[mighty asker]

Thanks.
But since multimap has value_compare member I could do it different way. Right?