I researched and implemented this last semester for a game development course. Hopefully this sample code can point you in the right direction of how you might approach this.
class Entity {
public:
Entity(const unsigned int id, const std::string& enttype);
~Entity();
//Component Interface
const Component* GetComponent(const std::string& family) const;
void SetComponent(Component* newComp);
void RemoveComponent(const std::string& family);
void ClearComponents();
//Property Interface
bool HasProperty(const std::string& propName) const;
template<class T> T& GetPropertyDataPtr(const std::string& propName);
template<class T> const T& GetPropertyDataPtr(const std::string& propName) const;
//Entity Interface
const unsigned int GetID() const;
void Update(float dt);
private:
void RemoveProperty(const std::string& propName);
void ClearProperties();
template<class T> void AddProperty(const std::string& propName);
template<class T> Property<T>* GetProperty(const std::string& propName);
template<class T> const Property<T>* GetProperty(const std::string& propName) const;
unsigned int m_Id;
std::map<const string, IProperty*> m_Properties;
std::map<const string, Component*> m_Components;
};
Components specify behavior and operate on properties. Properties are shared between all components by a reference and get updates for free. This means no large overhead for message passing. If there's any questions I'll try to answer as best I can.