How do I add optional functionality to a class?

Question

I'm currently trying to learn the ins and outs of XNA/C# but I'm currently stuck on a problem: I want to add optional functionality to a class and I have no idea how to even start. For clarity, here is my current code:

public class Actor
{
    //Fields
    private Vector3 m_location;

    //Properties
    public Vector3 Location
    {
        get { return m_location; }
        set { m_location = value; }
    }

    //Constructors
    public Actor(float x, float y, float z)
    {
        Location = new Vector3(x, y, z);
    }
    public Actor(Vector3 location)
    {
        Location = location;
    }
}

public class Actor2D : Actor
{
    //Fields
    private Texture2D m_texture;

    //Properties
    public Texture2D Texture
    {
        get { return m_texture; }
        set { m_texture = value; }
    }

    //Constructors
    public Actor2D(float x, float y, float z) : base(x, y, z) {}
    public Actor2D(Vector3 vector) : base(vector) {}

    //Methods
    public void Draw(SpriteBatch spriteBatch)
    {
        spriteBatch.Draw(Texture, new Vector2(Location.X, Location.Y), Color.White);
    }
    public void Load(ContentManager content, string asset)
    {
        Texture = content.Load<Texture2D>(asset);
    }
}

The logic here is that all Actors have to have a location but they don't necessarily have to have a texture as an Actor could be a light source, trigger, etc etc. Actor2D is similar in this except that it's designated as an Actor that uses 2D texture. What I want to do is have the ability to add functionality to either of these classes on an as needed basis. Say I want the Actor2D to be animated or as mentioned earlier I want to add a trigger or light source to an untextured Actor... What are some ideas that would help me accomplish these goals?

Answer 1

You could try taking a look at the decorator pattern, which allows you to 'tack on' behaviour to an object.