Re: communication between classes

On Apr 17, 1:42 pm, carvalho.mig...@gmail.com wrote:


What you want here is to implement the MVC pattern
http://en.wikipedia.org/wiki/Model-view-controller.
The Controller is the mouse and keyboard event handler. The View
portion are object that implement cg::Draw. The Model portion is stuff
that implements cg::Entity. Normally this is separated into two
different classes so you could have more than one View per Model (i.e.
more than one perspective on a Ship) but in your case putting them
both in the same class is fine.
When Views and Models are created, they register themselves with the
Controller, specifying which events they are interested in. (Using the
Vistor pattern may also help with this part http://en.wikipedia.org/wiki/Visitor_pattern).
The Model and Views also shared pointers to each other.
So you may have:
struct Event{
//info about the event
};

struct IListener{
virtual void onEvent(Event const&)=0;
};

Then
class Ship : public cg::Entity, public cg::IDraw, public IListener

and whatever class processes keyboard clicks and such would have a
container that maintains a bunch of poitners to IListeners
enum EventType{};//different sorts of events
struct IEventProcessor{
virtual void add(IListener* , EventType)=0;
virtual void remove(IListener* , EventType)=0;
};
So on each event type that contaner is scanned and onEvent is called.

I have no idea on how to register of keypresses and such in opengl,
you will have to figure out that part. Also, in real life I use
shared_ptrs instead of raw pointers, plus I would not use pointers as
the ObjectId as I did here (it would looke more like

struct IObject{
virtual ObjectId get_id()const=0;
};
struct IListener:virtual IObject{
virtual void onEvent(Event const&)=0;
};
struct IEventProcessor:virtual IObject{
virtual void add(shared_ptr<IListener>const& , EventType)=0;
//do nothing on duplicate Id
virtual void remove(ObjectId , EventType)=0;
};

but setting all this up is way overkill for a student Asteroids game

Good Luck
Lance

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