Vectors

This is a discussion on Vectors within the C++ Programming forums, part of the General Programming Boards category; I cannot seem to figure out how to pass by reference my vector of pointers. I think I am doing ...

  1. #1
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    Vectors

    I cannot seem to figure out how to pass by reference my vector of pointers. I think I am doing it right and I have tried searching google/ the forums, but I am at a loss.

    Here is my code

    Code:
    	std::vector<baseGameState*> States;
    	States.push_back(new MENU_STATE);
    So that should basically be a vector of pointers to objects that are gamestates if I did that correctly.

    Code:
    			if ((active && States.back()->run(States)) || keys[VK_ESCAPE])	// Active?  Was There A Quit Received?
    			{
    				done=TRUE;										// ESC or DrawGLScene Signalled A Quit
    			}
    In that part of the code I go to the most current vector and run it while passing States. But I am not sure if I am passing it as a reference or is it being copied.(If I try run(&States) it gives me an error message)

    Code:
    	int run(std::vector<baseGameState*>& States){
    		update();
    		render();
    		return 0;
    		};
    And this is what gets the reference I think, But I cannot seem to be able to push anything in the class.

    Can someone help me?

  2. #2
    C++ Witch laserlight's Avatar
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    In that part of the code I go to the most current vector and run it while passing States. But I am not sure if I am passing it as a reference or is it being copied.
    You are passing by reference, assuming that the function definition you show for run() is a member function of baseGameState. However, you do not appear to be actually using the States argument in run().
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    States is a private variable used by update to push/pop additional states.

    Code:
    class MENU_STATE: public baseGameState{
    private:											//All of our variables that the update function and render need
    	GLfloat	roll;									// Rolling Texture
    	int selector, max_selector,selected;
    	GLubyte Ycolor,fadeoutcolor;
    	GLfloat yOffset;
    	bool	Boolarrow[4];							//0=up
    													//1=down
    													//2=left
    													//3=right
    	DWORD TimeP[4];									//0=up
    													//1=down
    													//2=left
    													//3=right
    	Texture texture[2];												// Storage For 2 Textures ( NEW )
    	bool colordown;
    	std::vector<baseGameState*> States;
    	bool fadeout,fadeoutdone;
    protected:
    	int render();
    	int update();
    public:
    	MENU_STATE::MENU_STATE();
    	int run(std::vector<baseGameState*>& States){
    		update();
    		render();
    		return 0;
    		};
    	int resize();
    };

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    Uhh, so you have a private variable named States and you also make run take a parameter named States? What's the point here?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    I was trying to make it so that States(private) would get the reference, but I guess that is where my code is screwing up.

  6. #6
    C++まいる!Cをこわせ! Elysia's Avatar
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    You mean that your private States should be a reference bound to some other States somewhere else?
    If so, then you must initialize it, and you must do that in the initializer list that's in the constructors.
    If that's not an option, you'll have to use a pointer.

    I think I'm getting this correctly.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Yea it should be bound to the one in the Main() but I have no idea on how to do it

    edit(Just to clarify): basically I want to be able to modify my original vector from within my classes.
    Last edited by Shadowwoelf; 09-28-2008 at 09:10 AM.

  8. #8
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by Shadowwoelf View Post
    edit(Just to clarify): basically I want to be able to modify my original vector from within my classes.
    Yes, that's what I thought.
    But have you considered that baseGameState should have its own State vector? After all, the engine should own the states.
    It will also save you headache with pointers and references.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Well I am confused on what you mean by its own vector.

  10. #10
    C++まいる!Cをこわせ! Elysia's Avatar
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    std::vector<baseGameState*> States;
    Not a reference.
    Not a pointer.
    An instance of a vector which stores baseGameState pointers.

    It's the question of ownership - who owns the game states?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  11. #11
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    Right now that vector is in the Main().

  12. #12
    C++まいる!Cをこわせ! Elysia's Avatar
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    Yes, but why is it in main?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  13. #13
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    What Elysia is trying to say is:
    Think about where things are, and if you need it somewhere other than where it is visible at the moment, who [1] actually OWNS that data, and how do you get the data to the


    [1] "who" here means a function or object - not a person!

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    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  14. #14
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    Well the game I set my gameloop up I need the vector to be in main.

    Code:
    	while(done!=TRUE)												// Loop That Runs While done=FALSE
    	{
    		if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))				// Is There A Message Waiting?
    		{
    			if (msg.message==WM_QUIT)							// Have We Received A Quit Message?
    			{
    				done=TRUE;										// If So done=TRUE
    			}
    			else												// If Not, Deal With Window Messages
    			{
    				TranslateMessage(&msg);							// Translate The Message
    				DispatchMessage(&msg);							// Dispatch The Message
    			}
    		}
    		else													// If There Are No Messages
    		{
    		if(resize==true){
    				States.back()->resize();
    				resize=false;
    			}
    			ElapsedTime = timeGetTime()- LastTime;
    			if(ElapsedTime < DesiredFrameLength)
    			{
    				Sleep(DesiredFrameLength - ElapsedTime);
    				ElapsedTime = DesiredFrameLength;
    			}
    			LastTime = timeGetTime();
    			// Draw The Scene.  Watch For ESC Key And Quit Messages From DrawGLScene()
    			if ((active && States.back()->run(States)) || keys[VK_ESCAPE])	// Active?  Was There A Quit Received?
    			{
    				done=TRUE;										// ESC or DrawGLScene Signalled A Quit
    			}
    			else												// Not Time To Quit, Update Screen
    			{
    				SwapBuffers(hDC);								// Swap Buffers (Double Buffering)
    			}
    This way I can always add any new class onto the vector and not have to change anything in the gameloop.

    edit: Now that I think about it I could make a class to handle the other classes I suppose and use that in my gameloop. Was that what you guys were getting at?
    Last edited by Shadowwoelf; 09-29-2008 at 10:24 AM.

  15. #15
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by Shadowwoelf View Post
    edit: Now that I think about it I could make a class to handle the other classes I suppose and use that in my gameloop. Was that what you guys were getting at?
    Yes. Something like that.
    You can just create your engine class and call engine->run() and let it do everything.
    Then you only need one copy of the game states, and no reference in the class or main! Brilliant!
    Right?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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