Question

So, a quick summary of why I’m trying to do this:

I’m making a space flight program, wherein (once I code in more than one ship) I will be able to store different ships, e.g. craft[HAB], craft[AYSE], craft[ISS], and so forth. At the moment, I have only coded in one ship, and I declare it like so:

enum craft {HAB, CRAFTMAX};
...
[declaring ship class here]
...
ship craft[CRAFTMAX];

However, not all ships will be the same structure. For example, HAB (short for Habitat) will be a circle with three engine pods on the bottom, AYSE will be a space station with a tube going to the centre, and docking lights, and so forth. I am making these functions draw a vector to the screen.

At the moment, I have declared ship::draw, and I just use this to draw the Hab. However, I want to be able to modify each draw function to draw that ship, i.e. craft[AYSE].draw() will have a different declaration than craft[HAB].draw().

I’ve thought, and looked up different ways to do this, but I haven’t gotten much success. I’d still like to be able to iterate through all the crafts for ease of calculating gravity and collisions. But I’m guessing if it’s impossible to individually declare functions when they are elements of an array, it won’t be too much trouble to declare each ship individually, as there will only be 10, max.

Here is my git repository that is storing this, if you want to take a look at any other code. It is definitely a bit unorganized, as it is a monopoly project, and I only ever see myself using it.

Any of you tried to do this? I’m sure there must be a few people out there!

And thanks in advance.

Answer 1

I think you will be much better by using a base class for a Ship object, then deriving from this base class for the different types of ships. Then use some container that allows you to iterate through all ship objects and call the respective functions. Like:

class Ship {
public:
  virtual void draw() const = 0;
};

class HAB : public Ship {
  virtual void draw() const;
};

class AYSE : public Ship {
  virtual void draw() const;
};

Then using a container like:

vector<Ship> ships;
ship.insert(HAB());
ship.insert(AYSE());

// to draw
for_each(ships.begin(), ships.end(), mem_fn(&Ship::draw));

I came up with this fairly quick so you will have to work out the details. The way you are thinking of doing it is not very OO and will have problems in terms of maintenance (think Single Point of Maintenance).