Entity Manager System : C++

#include <iostream>
#include <vector>

template <class M = std::string, class E = int>
E log(M msg, E error = 0)
{
    std::cout << msg;
    return error;
}


struct CollisionInfo
{
    int _id1 = 0;
    int _id2 = 0;

};

struct Entity
{
    int _id = 0;

    int _x = 0;
    int _y = 0;

    std::string _name = "";

    Entity(std::string name, int id = 0)
    {
        _id = id;
        _name = name;
        log ("- Monster created !\n");
    }

    virtual~Entity()
    {
        log("- Monster deleted !\n");
    }

    void update()
    {

    }


    void render()
    {
        std::cout << " : _id = "<< _id << " : _name = "<< _name << "\n";
    }


};

struct EntityManager
{
    std::vector<Entity*> _vecEntity;
    std::vector<int> _vecFreeEntity;



    EntityManager()
    {

    }
    virtual ~EntityManager()
    {
        // clean vector
        for (auto & it: _vecEntity)
        {
            if (it != nullptr)
            {
                delete it;
                it = nullptr;
            }
        }
        _vecEntity.clear();

        _vecFreeEntity.clear();

    }

    void add(Entity *entity)
    {
        if (entity != nullptr)
        {
            if (!_vecFreeEntity.empty())
            {
                int freeEntityIndex = _vecFreeEntity.back();
                _vecFreeEntity.pop_back();

                _vecEntity[freeEntityIndex] = entity;
                entity->_id = freeEntityIndex;

            }
            else
            {
                int id = _vecEntity.size();
                entity->_id = id;
                _vecEntity.push_back(entity);
            }
        }
    }

    void del(int id)
    {
        if (id > -1 && id < _vecEntity.size())
            if (_vecEntity[id] != nullptr)
            {
                delete _vecEntity[id];
                _vecEntity[id] = nullptr;

                _vecFreeEntity.push_back(id);
            }
    }

    int get(int id)
    {
        return _vecEntity[id]->_id;
    }

    int idByName(std::string name)
    {
        for (auto & it: _vecEntity)
        {
            if (it != nullptr)
                if (it->_name == name)
                    return it->_id;
        }

        return -1;
    }

    void update()
    {

    }


    void render()
    {

    }


};



bool CollideEntity(Entity *e1, Entity *e2, CollisionInfo &info)
{

    if (e1->_x == e2->_x &&
        e1->_y == e2->_y)
    {


        return true;
    }

    return false;
}

int main()
{
    EntityManager *_manEntity = new EntityManager();

    for (unsigned i = 0; i < 5; i++)
    {

        _manEntity->add(new Entity("Mugen"));
        //unsigned index = _vecEntity.size(); // get the current index ;
        //_vecEntity.push_back(new Entity("Monster", _vecEntity.size()));

    }

    _manEntity->del(2);
    _manEntity->del(10);
    _manEntity->del(3);

    _manEntity->add(new Entity("Silver"));
    _manEntity->add(new Entity("Chrome"));
    _manEntity->add(new Entity("Opera"));
    _manEntity->add(new Entity("brandon"));
    _manEntity->add(new Entity("FireFox"));

//    _manEntity->del(_manEntity->idByName("Opera"));
//    _manEntity->del(_manEntity->idByName("FireFox"));

    for (unsigned index = 0; index < _manEntity->_vecEntity.size(); index++)
    {
        if (_manEntity->_vecEntity[index] != nullptr)
        {
            std::cout << "index = "<<  index;
            _manEntity->_vecEntity[index]->render();
        }
    }


    if (_manEntity->idByName("Chrome") != -1)
        std::cout << "--- index = _id of Chrome = "<< _manEntity->idByName("Chrome") << "\n";

    // colision test
//    for (unsigned i = 0; i < _manEntity->_vecEntity.size(); i++)
//    {
//        for (unsigned j = i+1; j < _manEntity->_vecEntity.size(); j++)
//        {
//
//        }
//    }

    delete _manEntity;

    return log("--- End of main ---");
}