"The C++ Library doesen't provide a hash for this type." - 在 std：：unordered_map 中使用自己的类

我正在尝试编写康威的"生命游戏"。在接近我的目标时，我遇到了编译器错误：

C2338： C++库不提供此类型的哈希。

起初我使用 SFML 类sf::Vector2D.当它对我不起作用时，我编写了一个自己的类，希望我可以实现缺少的hashCode方法。

我的问题是：
是否可以使用我自己的类和自己的hashCode方法来std::unordered_map？我需要使用一个可以容纳两个数字的类。(我也尝试了std::tuple，struct之类的)。

这是我的一张代码：

#include "GameMechanics.h"

GameMechanics::GameMechanics(Elements * elements):elements(elements)
{
this->refreshTime = 1000000;    //ms
this->clock.restart();
}

GameMechanics::~GameMechanics()
{
}
bool GameMechanics::isRunning()
{
return this->running;
}
void GameMechanics::setRunning(bool running)
{
this->running = running;
}
void GameMechanics::loop()
{
unsigned passedTime = clock.getElapsedTime().asMicroseconds();  //check passed time since the clock got restarted
this->timeHeap  +=  passedTime; //add passed time to the timeheap
this->clock.restart();
//only refresh every "refreshTime" seconds
if (timeHeap >= this->refreshTime) {    
std::cout << "Calculated new generation!" << std::endl;
this->timeHeap -= this->refreshTime;
this->calculateNextGeneration();
}
}
void GameMechanics::calculateNextGeneration()
{
std::list<sf::Vector2i> oldGeneration = this->elements->getElements();  //  population in the moment
sf::Vector2u elements = this->elements->getElementCount();
std::unordered_map<MyVector2D, int> counter;     //here is the problem. Thats the line that makes some trouble

for (std::list<sf::Vector2i>::iterator it = oldGeneration.begin(); it != oldGeneration.end(); it++) {
sf::Vector2i position = *it;
for (int i = -1; i < 2; i++) 
{
for (int j = -1; j < 2; j++) 
{
if (position.x + i >= 0 && position.x + i <= this->elements->getElementCount().x &&
position.y + j >= 0 && position.y + j <= this->elements->getElementCount().y) 
{
if (counter.find(MyVector2D(position.x + i, position.y + j)) != counter.end()) 
{
counter.at(MyVector2D(position.x + i, position.y + j))++;
}
else //if there is no such element, create a new entry
{
counter.insert({ MyVector2D(position.x + i, position.y + j),1 });
}
}
}
}
}

//create new generation
this->brithNewGeneration(&counter);
}
void GameMechanics::brithNewGeneration(std::unordered_map<MyVector2D,int>* counter)
{
//this methode does work
std::list<sf::Vector2i> newGeneration;
//  for (std::unordered_map<MyVector2D, int>::iterator it = counter->begin(); it != counter->end(); it++) 
{
//if life vell with < 2 neighbours, it dies
//life cell with 2 or 3 neighbours will continue living
//life cell with >4 cells will die
//dead cell with 3 neighbours will start living
}
}