Elysian Shadows

hello everybody this is my first question in the Programming Discussion !
i hope this is seen as an valid nobby question here in this forum ^^

i have created 2 classes and 1 function.
my function checks one variable from class 1 and one variable from class 2 : function("variable_from_class1", "variable_from_class2") the function returns a boolian value (but that doesn't matter).

my problem is that i have different functionmembers in class 1 and one of those members checks my function (with the "variable_from_class1" and "variable_from_class2") so i get an error that i have
to declare "the variable_from_class2".

what can i do ?

thank you guys


edit: ok i used a global variable this time but isn't there any other chance to import a class member to another ? maybe with class friendship ? ^^

I'm not sure I understand, you should post some code. Include the classes and the where you are calling the function.

Yeah, post your code. There's a clear misunderstanding about how passing parameters to functions work.

uhhh...now this is gonna be awkward ^^
i was studieng a bit of lazy foos sdl tutorial (although i'm aware that i don't feel 100% comfortable with c++..especially classes & pointers)
anyway here is the modified code:

it's a bit much code but these are the two classes "Char" and "Collision" and the function check_collision


SDL_Rect colli; <-- this is how i solved it i use a global variable to hold the information from the class "Collision"

class Char
{
private:
SDL_Rect box;
int xvel;
int yvel;
int frame;
int status;

public:
Char();
void handle_events();
void move();
void show();
void set_camera();
};


void Char::move()
{

//Move
box.x += xvel;

//Keep the stick figure in bounds
if( ( box.x < 0 ) || ( (box.x + CHAR_WIDTH) > LEVEL_WIDTH ) || ( check_collision( box, colli ) )) <--- so now here: i first hat a local but public variable from the function "Collision" instead of the global variable "colli"
{
box.x -= xvel;
}

box.y += yvel;

if( ( box.y < 0) || ( (box.y + CHAR_HEIGHT) > LEVEL_HEIGHT ) || ( check_collision( box, colli ) ))
{
box.y -= yvel;
}





class Collision
{

public:
//Constructor
Collision();
Collision(int, int, int, int);

void showcollision();

};

Collision::Collision()
{
colli.x = 470;
colli.y = 350;
colli.w = 40;
colli.h = 32;
}
Collision::Collision(int a, int b, int c, int d)
{
colli.x = a;
colli.y = b;
colli.w = c;
colli.h = d;
}





bool check_collision( SDL_Rect Char, SDL_Rect Collision )
{
//The sides of the rectangles
int leftChar, leftCollision;
int rightChar, rightCollision;
int topChar, topCollision;
int bottomChar, bottomCollision;

//Calculate the sides of rect A
leftChar = Char.x;
rightChar = Char.x + Char.w;
topChar = Char.y;
bottomChar = Char.y + Char.h;

//Calculate the sides of rect B
leftCollision = Collision.x;
rightCollision = Collision.x + Collision.w;
topCollision = Collision.y;
bottomCollision = Collision.y + Collision.h;

//If any of the sides from A are outside of B
if( bottomChar <= topCollision )
{
return false;
}

if( topChar >= bottomCollision )
{
return false;
}

if( rightChar <= leftCollision )
{
return false;
}

if( leftChar >= rightCollision )
{
return false;
}

//If none of the sides from A are outside B
return true;
}



and i was just wondering if there is a better way instead of using a global variable since i heard in objective programming you should use as less globals as possible to prevent errors in code etc.
isn't there an other way of passing a variable (or any other member) of a class to another class ?

You could make the Char class a friend by putting this inside Collision: This will allow member functions of Char to access private members of Collision.

aha friend class .. i guess that is what i need !
unfortunately it doesn't work for me could you show me where exactly i have to write it in ? inside "private" or "public:" ? ^^; thx !

edit: don't bother i'll just read about friend classes, thank you anyways !

chrizZz wrote:aha friend class .. i guess that is what i need !
unfortunately it doesn't work for me could you show me where exactly i have to write it in ? inside "private" or "public:" ? ^^; thx !

edit: don't bother i'll just read about friend classes, thank you anyways !

No problem. And I'm pretty sure the friend class declaration goes in "private".

Hey just to tell you, It's easier to put your code in the code boxes, just hit the code button above the post a reply box, and place your code between the ["code"] ["/code"] things... take out the quotes though.

alright i'll keep in mind for the next time (im sure there will^^) thx 4 info !

Limit your use of friends. Implement a public accessor method in your class that returns the value of whatever variable you want.