instance of a class disappearing after function ends

i know that this is a simple question, and i know that theres a simple answer, but for the life of me i cant remember how to do it. basically, i have a class (called AgentClass), and as im using a graphics library called GameX there is a function called on startup called GameInit. In this function goes all initialisation code, including where i am attempting to make a whole bunch of instances of my AgentClass class. i have a linked list type thingy in place to cycle through them all, and the pointers for this are all working fine (i have several instances created outside any function which work fine).

Basically, any instance of my class created in this function disappears as soon as the function returns. I have checked this by putting a little thing in the deconstructor which lets me know when the instance is removed - and they are being deleted at the end of the function.

currently to create an instance i do:

Code:

---

AgentClass myAgent(100,100,...other params...);

---

so... what do i do to stop them disappearing after the function returns?

thanks so much for any help, i know this is an easy question...

You can create the object before calling the function, and then pass the object to the function by reference.

If you declare your class variable inside your class, then you can't use it elsewhere anyway.
So if you only need it to stay in that function till the program ends, use static.

Oh, I read it again, and realised my mistake: you are specifically creating the objects in this function. What I wrote does not apply.

every thing in function will end as the functions end :)

You need to create them on the heap with new. Don't forget to delete them in GameDeinit().

Statics are good...

Code:

---

#include<iostream>
class Fruit{
        public:
                int size;
                Fruit();
};
Fruit::Fruit(){
        size=0;
}
int FruitSize(){
        static Fruit apple;
        if(apple.size==0){
                printf("The apple was not loaded, loading.\n");
                apple.size=1;
        }
        else{
                printf("The apple is already loaded.\n");
        }
}
int main(){
        FruitSize();
        FruitSize();
        FruitSize();
        FruitSize();
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(),'\n');
}

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But not in this case. If GameInit() is supposed to set up the data for the entire game, then it really shouldn't keep that data as statics. It would actually be more appropriate to make it global, then.

cheers for all the replies, nice to have such an active forum...

creating them on the heap, i assume that gives me pointers to the location? i can deal with that. then i have to make sure to free all the memory at the end, right?

isnt there an easier way to do this? im sure ive done it once before - created lots of objects in a given function which can then be accessed anywhere else in the program - but i cant remember how. maybe i was allocating each of them memory...

i think cornedbee is onto it - can global be used from inside a function?

>can global be used from inside a function?
Unless you hide it with a local variable of the same name, yes.

Quote:

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Originally Posted by Prelude

>can global be used from inside a function?
Unless you hide it with a local variable of the same name, yes.

---

Can't you still use :: to access the global and differentiate it from the local?

Code:

---

int x = 0;  // Global

void foo()
{
    int x = 5;  // Local

    cout << "Local x: " << x << endl;
    cout << "Global x: " << ::x << endl;
}

---

Thought you could do that.

can a global be declared from inside a function, though? sorry i probably should have said it more clearly to start with...

Quote:

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Originally Posted by combatdave

can a global be declared from inside a function, though? sorry i probably should have said it more clearly to start with...

---

The global can be referenced from within a function, but it cannot be declared inside the function... that would make it a local variable (local to the function in question) and not global.

I considered suggesting some kind of singleton to which you can add AgentClass objects in GameInit(), and from which you can remove them, but that design may not be very good. CornedBee's suggestion sounds simpler though, but can you just return a pointer from GameInit(), or change its signature (e.g., pass a pointer by reference)?

Urgh!

Meh. Pass a reference to the GameState object that contains everything the game needs as members.

Better yet, just instantiate the GameState object and replace GameInit with GameState's constructor. Replace GameDeinit() with the destructor. Create a single GameInit instance in WinMain/main and let C++ handle the rest.
Init/Deinit function pairs are sooo C. ;)