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Communicating through objects

Mybowlcut · 2008-02-06T18:55:11

Hey. I have just changed my whole structure for dealing with Images. Now each Image draws itself and updates itself (if it's a Button and the mouse is over it, it will change to an OVER state, etc.). Because I changed this... a lot of other things got changed. Now I'm left with objects that maintain themselves, which is great... but I don't know how to get anything from these objects... such as determining when to start a new game, view the instructions, etc: RETURN_CODE menu(Draw_Engine& DE, Audio_Engine& AE, SDL_Event& event_) { // Create the menu screen. Screen menu_screen("Screens/Menu_Screen/"); bool exit_game = false; while(!exit_game) { // While the user hasn't exit while(SDL_PollEvent(&event_)) { // While there's events to handle if(event_.type == SDL_QUIT) { // If the user has Xed out exit_game = true; break; } // if user pressed "new game" // call game() // else if user pressed "instructions" // call instructions() // else if user pressed "exit" // exit game menu_screen.Update(event_); menu_screen.Draw(DE.Get_Screen()); if(!DE.Draw_Screen()) { return RC_ERROR; } } } return RC_EXIT_PROGRAM; } class Screen : public Drawable, public Updateable, public Uncopyable { public: Screen(); Screen(const std::string& directory); virtual ~Screen(); virtual void Draw(SDL_Surface* screen); virtual void Update(const SDL_Event& event_); protected: virtual void Load(const std::string& directory); std::vector<Base_XImage*> elements; }; class Base_XImage : public Drawable, public Updateable, public Cloneable { public: Base_XImage(); Base_XImage( const std::string& file_name_, int position_x, int position_y, bool is_colour_key_, SDL_Colour colour_key_ = SDL_Wrappers::colour(0,0,0)); Base_XImage(const Base_XImage& rhs); virtual ~Base_XImage(); Base_XImage& operator=(const Base_XImage& rhs); const std::string& Get_File_Name() const; const SDL_Rect& Get_Position() const; bool Is_Colour_Key() const; const SDL_Colour& Get_Colour_Key() const; virtual void Load(); virtual void Draw(SDL_Surface* screen) = 0; virtual void Update(const SDL_Event& event_) = 0; virtual Base_XImage* Clone() const = 0; protected: static void Check_Opening_Tag(const std::string& buffer); static void Check_Closing_Tag(const std::string& buffer); std::string file_name; SDL_Rect position; bool is_colour_key; SDL_Colour colour_key; SDL_Surface* surface; }; I don't really want to have huge switch statements throughout my code checking to see if a certain button was pressed to start a new game... so I was wondering if anyone has a solution to this? Perhaps a Listener class or something? I'm really not that great with patterns/design like this and so I'm relying greatly on the suggestions of posters. Cheers.

General and Gameplay Programming Programming

Started by Mybowlcut February 06, 2008 01:29 AM

13 comments, last by Mybowlcut 16 years, 2 months ago

Mybowlcut

176

Author

February 06, 2008 09:14 AM

Quote:Original post by phantom
Depends on how you are doing your input, however for the sake of arguement lets say you are using a mouse, the steps would be;

- Detect mouse event (I recommend 'mouse up' as that's how GUIs like Windows work)
- Find out which component is under the mouse when the even happens
- Call the component's "selected" event function

This 'selected' function will then do the work of "somehow" moving the game to the selected screen (game, instructions, etc).

This button class derives from Base_XImage and this particular function would be the "event" function that you mentioned:

void XButton::Update(const SDL_Event& event_){	const SDL_Rect mouse = {event_.motion.x, event_.motion.y};	if(Is_Mouse_Over(mouse))	{		switch(event_.type)		{		case SDL_MOUSEMOTION:			if(current_state == DOWN)				break;			Set_Current_State(OVER);			break;		case SDL_MOUSEBUTTONDOWN:			Set_Current_State(DOWN);			break;		case SDL_MOUSEBUTTONUP:			Set_Current_State(OVER);			break;		}	}	else		Set_Current_State(OFF);}

I've got that.. but I'm unsure of how/why I'd start a game from inside a Button's Update function. :(

_the_phantom_

11,263

February 06, 2008 09:20 AM

Well, you wouldn't have to, this comes back to what was said earlier in the thread about observers.

The process goes something like;

- App tells button it has been pressed
- Button then tells everyone on its observer list that it has been pressed
- Observers go off and act on that happening

The observers could do anything from load a script to kick the game off, to create a new 'game' object and kick of it's 'run' function or whatever it is required to do to act on the button being pressed.

Mybowlcut

176

Author

February 06, 2008 09:45 AM

Ok, I'm working on that now. But I've got an error whilst testing:

void Screen::Notify(Observable* observable, void* oe){	Base_XImage::OBSERVABLE_EVENT* event_ = (Base_XImage::OBSERVABLE_EVENT*)oe;	switch(*event_)	{	case Base_XImage::LMB_CLICK:		std::cout << "Left mouse click!" << std::endl;		break;	case Base_XImage::RMB_CLICK:		std::cout << "Right mouse click!" << std::endl;		break;	case Base_XImage::MOUSE_OVER:		std::cout << "Mouse over!" << std::endl;		break;	}}

Quote:First-chance exception at 0x0041612c in SDL_Testing.exe: 0xC0000005: Access violation reading location 0x00000002.

I'm calling it like this:

Notify_Observers(this, (void*)MOUSE_OVER);

Is it because it's a constant/literal? If so, how would I get around it?

Gage64

1,235

February 06, 2008 01:53 PM

Change this:

Notify_Observers(this, (void*)MOUSE_OVER);

to this:

int e = (int)MOUSE_OVER;Notify_Observers(this, (void*)&e);

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Mybowlcut

176

Author

February 06, 2008 06:55 PM

Ok. Just out of curiosity, why? Could I replace int e with the enum type?

OBSERVABLE_EVENT e = MOUSE_OVER;Notify_Observers(this, (void*)&e);

Edit: Woohoo! It's working now! Thanks, Gage!

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