Component based architecture c++ - c++

Question

I'm having trouble figuring out a way to make a component based engine architecture in c++. But i cant figure out a way to combine a vector of components with a class that derives from component.
I want to override components virtual function. But the only way i can make it call the overrided function is to make the component-derived class a pointer, but i want every gameobject to contain its own components in a vector and not outside the class as a pointer.
I tried to remove as much unnecessary code as possible.
My structure:
//GameObject class, contains components and other objects
class GameObject
{
public:
GameObject(){}
~GameObject(){}
void AddChild(GameObject child)
{
children.push_back(child);
}
void AddComponent(Component component)
{
components.push_back(component);
}
void Input(){}
void Update(){}
void Render()
{
for(unsigned int i = 0; i < components.size(); i++)
components[i].Render();
}
private:
std::vector<GameObject> children;
std::vector<Component> components;
};
//base class component
class Component
{
public:
Component(){}
~Component(){}
virtual void Input(){}
virtual void Update(){}
virtual void Render(){ cout << "Component -> Render()" << endl; }
};
class MeshRenderer : public Component
{
public:
MeshRenderer(Mesh _mesh, Material _material)
{
mesh = _mesh;
material = _material
}
~MeshRenderer(){}
//override components virtual Render()
void Render(Transform transform)
{
mesh.Render(material);
cout << "MeshRenderer -> Render()" << endl;
}
private:
Mesh mesh;
Material material;
};
GameObject* root = new GameObject();
MeshRenderer meshRenderer(mesh, material);
root->AddComponent(meshRenderer);
//GameLoop
while(!quit)
{
root->Render();
}

Answer 1

It would be the best if you could use unique_ptr:
void AddComponent(std::unique_ptr<Component> component) {
components.push_back(std::move(component));
}
std::vector<std::unique_ptr<Component>> components;
Thus by calling AddComponent() you transfer ownership of the component to containing GameObject.

Answer 2

Looks like you want to pass your objects by reference, use
void AddComponent(Component& component);
to avoid any slicing.
For proper usage with std::vector<>'s and polymorphic inheritance, you'll need smart pointers, e.g. std::unique_ptr<Component> to preserve ownership, or std::shared_ptr<Component> for shared ownership (raw pointers as Component* might work as well, but are far harder to manage correctly).
void AddComponent(std::unique_ptr<Component> componentPtr); // Unique ownership
or
void AddComponent(std::shared_ptr<Component> componentPtr); // Shared ownership
and accordingly
std::vector<std::unique_ptr<Component>> components;
or
std::vector<std::shared_ptr<Component>> components;
It depends on your actual use cases if these Component instances should be uniquely owned by their aggregating parent GameObject class, or not.
To use std::shared<> pointers, that could expire outside their usages scope you may consider using std::weak_ptr<>.
As mentioned, it totally depends on your use cases, and how you want these aggregated components being accessible from outside of the GameObject class.