class CItem
{
/* This is the class that will hold the description as well as the functions to print the descrition to the screen.*/
};
void InitRoom1(void);
void DestroyRoom1(void);
void InitRoom1(void)
{
CItem Room();
CItem Poster();
/* Not sure what to do here, but I need some way of making the objects created above last outside this funtion.*/
}
void DestroyRoom1(void)
{
//This will destroy all objects once I am done with that room
}
int main()
{
int lookingat; /*this keeps track of what object they are looking at*/
InitRoom1(); //Initilize the room
switch(lookingat)
{
/* How do I keep the objects alive so I can use them here? I don't want to make them static, becasue I want to be able to destroy them.*/
case 1: room.printdesc();
break;
case 2: posterprintdesc();
break;
default: cout << "What are you looking at?";
}
DestroyRoom1();
return 0;
}
operator new
Author
I am trying to create a game that has many different rooms. Each room will have several objects that contain a description of the object, as well as a few functions that format the description and display it on the screen. I want to create a function for each room that will initilize all the objects in that particular room. Once I exit the initilization function, I will want to call on the object members in a function that decides which room to display. Once I am done with that room, I will destroy all the objects. I know I am going to need to use the operator new, but the book I am learning from only has a few paragraphs on new. Can someone show me how to use new? Here is the code so you can see what I am talking about.
[Edited by - mrtie_dye on September 8, 2004 12:02:07 AM]
Author
I realized I had way too much code to describe what I was doing, so I simplified it some. Hope this helps.
Author
Quote:
CItem * items = new CItem[NUMITEMS];
items[index].function();
...
delete[] items;
I assumed that the first line goes in the InitRoom1 function, the second line goes in main, and the third line goes in the DestroyRoom1 function. When I do this, it gives me an undeclared identifier error for items in the DestroyRoom1 function and in main.
keep in mind that if you have this line in your initializtion funciton:
the code in your other functions will not be able to see it because it will not be in scope.
What you must do is place the declaration of items:
Somewhere that all of the functions can then see it.
In your case this would be as a globally accessable variable. You will probably want to just use a global. The following is a mockup of what I'm talking about:
edit: fixed code tags
CItem * items = new CItem[NUMITEMS];the code in your other functions will not be able to see it because it will not be in scope.
What you must do is place the declaration of items:
CItem *items;Somewhere that all of the functions can then see it.
In your case this would be as a globally accessable variable. You will probably want to just use a global. The following is a mockup of what I'm talking about:
struct some_class {};some_class *global_var;void InitGlobal(){ global_var = new some_class[100];}void UseGlobal(){ ... do something with global_var ...}void DestroyGlobal(){ delete[] global_var;}edit: fixed code tags
No, man(or woman), you either have to make items global or make it a member in a class. Because what you've done, is declared it inside a function. As soon as that function exits, items is no longer a valid identifier. Its gone out of scope.
EDIT: Darn, just missed it!
EDIT: Darn, just missed it!
Author
Thanks so much for your help. I am almost there. A strange thing happens, though, and I don't know how to find out why. I have included the full code below so you can put it into c++ and see the error message. If you look at the function SnakesRoom(), you will see where I delete pRoom on the last line of the function. If I comment this line out, the program runs fine. If I leave it there, it gives me some strange debug error. Any help would be greatly appreciated.
#include <iostream> #include <windows.h> #include <string> using namespace std;class CItem{private: char* pm_desc; int* charcount; static int state; public: CItem(char* desc, int charcounted) { pm_desc = new char[strlen(desc) + 1]; strcpy(pm_desc, desc); charcount = new int; *charcount = charcounted; } CItem() { } void DrawLine(string szText, int X, int Y, WORD color) { HANDLE OutputH; COORD position = {X, Y}; OutputH = GetStdHandle(STD_OUTPUT_HANDLE); SetConsoleTextAttribute(OutputH, color); SetConsoleCursorPosition(OutputH, position); cout << szText; } void DrawBorder() { int x = 3; int y = 2; DrawLine("*************************************************************************", x, y, FOREGROUND_BLUE); for(int i; y < 18; y++) { DrawLine("*", x, y,FOREGROUND_BLUE); } y = 3; x = 75; for(; y < 18; y++) { DrawLine("*", x, y,FOREGROUND_BLUE); } x= 3; DrawLine("*************************************************************************", x, y, FOREGROUND_BLUE); } void mf_printdesc() { int count = 60; int currentchar = 0; cout << endl << endl << endl; while(count < *charcount) { while(pm_desc[count] != ' ' || count > *charcount) count--; cout << endl << "\t"; for(;currentchar < count; currentchar++) { cout << pm_desc[currentchar]; } count += 60; } cout << endl << "\t"; for(; currentchar < *charcount; currentchar++) { cout << pm_desc[currentchar]; } DrawBorder(); DrawLine("Enter Command: ", 3, 20, FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE); delete[] pm_desc; delete charcount; } };void SnakesRoom(void);void InitSnakeRoom(CItem* pRoom);void SnakesRoom(void){ CItem* pRoom = new CItem[1]; InitSnakeRoom(pRoom); pRoom[0].mf_printdesc(); delete[] pRoom;}void InitSnakeRoom(CItem* pRoom){ char room[] = {" Description of the room. I have added this sentence in here just so you can see what the mf_printdesc function does."}; char poster[] = {" Description of a poster."}; char* proom = room; char* pposter = poster; int charcount; charcount = (sizeof room) / (sizeof room[0]); CItem Room(proom, charcount); charcount = (sizeof poster) / (sizeof poster[0]); CItem Poster(pposter, charcount); pRoom[0] = Room; pRoom[1] = Poster;}int main(){ SnakesRoom(); return 0;}
Its a bad idea to re-allocate your CItems every time you go in the room. Besides, do you really need to dynamically allocate them?
However, The error is coming up because you are only allocating 1 CItem, and you try to change 2 of them. Then on the delete, it causes an assertian failure.
To fix this, do this:
CItem * pRoom = new CItem[2]; //allocates 2 CItems
because later on, you do this:
//modifies 2 CItems, one of which was not allocated to you
pRoom[0] = Room;
pRoom[1] = Poster;
However, The error is coming up because you are only allocating 1 CItem, and you try to change 2 of them. Then on the delete, it causes an assertian failure.
To fix this, do this:
CItem * pRoom = new CItem[2]; //allocates 2 CItems
because later on, you do this:
//modifies 2 CItems, one of which was not allocated to you
pRoom[0] = Room;
pRoom[1] = Poster;
Quote:Original post by mrtie_dye
Thanks so much for your help. I am almost there. A strange thing happens, though, and I don't know how to find out why. I have included the full code below so you can put it into c++ and see the error message. If you look at the function SnakesRoom(), you will see where I delete pRoom on the last line of the function. If I comment this line out, the program runs fine. If I leave it there, it gives me some strange debug error. Any help would be greatly appreciated.
*** Source Snippet Removed ***
NO NO NO! when you are using C++, use it, not C! try this:
#include <iostream> #include <windows.h> #include <string> using namespace std; // this line is really shitty, use "using cout" insteadclass CItem{ // your CItem object};class SnakesRoom : public CItem{ // your SnakesRoom object};int main(){ SnakesRoom room1(); // nice return 0;}[Edited by - Triglav on September 8, 2004 3:19:34 AM]
Quote:Original post by Triglav
...
int main()
{
SnakesRoom room1(); // nice
return 0;
}
SnakesRoom room1(); is actually a function declaration, it doesnt create an instance of SnakesRoom .
SnakesRoom room1; //nicer
:)
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