Vector with smart pointers to inherited objects.

There is a base class GameObject

GameObject.h

 #pragma once #include "cocos2d.h" USING_NS_CC; class GameObject { public: GameObject(); GameObject(float x, float y, Vec2 direction); virtual ~GameObject(); virtual float getX(); virtual void setX(float value); virtual float getY(); virtual void setY(float value); virtual float getRotation(); virtual void setRotation(float value); virtual void rotateBy(float value); virtual void update(float deltaTime){}; protected: void calculateRotation(); float x; float y; float rotation; Vec2 direction; }; 

GameObject.cpp

 #include "GameObject.h" GameObject::GameObject():x(0), y(0), direction(0, 1), rotation(0) { } GameObject::GameObject(float x, float y, Vec2 direction):x(x), y(y), direction(direction), rotation(0) { } GameObject::~GameObject() { } float GameObject::getX() { return x; } void GameObject::setX(float value) { x = value; } float GameObject::getY() { return y; } void GameObject::setY(float value) { y = value; } float GameObject::getRotation() { return rotation; } void GameObject::setRotation(float value) { rotation = value; } void GameObject::rotateBy(float value) { direction.rotate(Vec2(0, 0), value); calculateRotation(); } void GameObject::calculateRotation() { rotation = MATH_RAD_TO_DEG(atan2f(direction.x, direction.y)); } 

The BulletModel class inherits from GameObject

BulletModel.h

 #pragma once #include "GameObject.h" class BulletModel: public GameObject { public: BulletModel(float x, float y, Vec2 direction); virtual ~BulletModel(); void update(float deltaTime); private: float speed; float damange; }; 

BulletModel.cpp

 #include "BulletModel.h" BulletModel::BulletModel(float x, float y, Vec2 direction):GameObject(x, y, direction) { } BulletModel::~BulletModel() { } void BulletModel::update(float deltaTime) { x += direction.x * speed * deltaTime; y += direction.y * speed * deltaTime; } 

The TankModel class TankModel inherited from Unit which is inherited from GameObject

Unit.h

 #pragma once #include "GameObject.h" class Unit: public GameObject { public: Unit(int health); virtual ~Unit(); virtual void update(float deltaTime) {}; protected: int health; }; 

Unit.cpp

 #include "Unit.h" Unit::Unit(int health):GameObject(), health(health) { } Unit::~Unit() { } 

TankModel.h

 #pragma once #include "Unit.h" class WorldModel; class TankModel: public Unit { public: TankModel(std::shared_ptr<WorldModel> world); virtual ~TankModel(); void thrust(float deltaTime); void backing(float deltaTime); void rotateLeft(float deltaTime); void rotateRight(float deltaTime); void shoot(float deltaTime); void update(float deltaTime); private: const float moveSpeed; const float rotationSpeed; std::shared_ptr<WorldModel> world; }; 

TankModel.cpp

 #include "WorldModel.h" #include "TankModel.h" #include "BulletModel.h" #include "GameScene.h" TankModel::TankModel(std::shared_ptr<WorldModel> world): Unit(100), moveSpeed(50), rotationSpeed(3), world(world) { } TankModel::~TankModel() { } void TankModel::thrust(float deltaTime) { x += direction.x * moveSpeed * deltaTime; y += direction.y * moveSpeed * deltaTime; } void TankModel::backing(float deltaTime) { x -= direction.x * moveSpeed * deltaTime; y -= direction.y * moveSpeed * deltaTime; } void TankModel::rotateLeft(float deltaTime) { rotateBy(rotationSpeed * deltaTime); } void TankModel::rotateRight(float deltaTime) { rotateBy(-rotationSpeed * deltaTime); } void TankModel::shoot(float deltaTime) { world->addBullet(x, y, direction); } void TankModel::update(float deltaTime) { } 

I create a container std::vector<std::shared_ptr<GameObject>> models;

Objects std::shared_ptr<TankModel> can be put into it, but objects std::shared_ptr<BulletModel> cannot be.

Gives an error message

 WorldModel.cpp(34): error C2664: 'void std::vector<std::shared_ptr<GameObject>,std::allocator<_Ty>>::push_back(const std::shared_ptr<GameObject> &)': cannot convert argument 1 from 'std::shared_ptr<BulletModel>' to 'std::shared_ptr<GameObject> &&' 2> with 2> [ 2> _Ty=std::shared_ptr<GameObject> 2> ] 2> WorldModel.cpp(34): note: Reason: cannot convert from 'std::shared_ptr<BulletModel>' to 'std::shared_ptr<GameObject>' 2> WorldModel.cpp(34): note: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 

Why?