Need to make an array of already created objects - c++

Question

I am making several items, and need to set them as being interactable with each other.
Item i1 = Item("Item 1");
Item i2 = Item("Item 2");
Item i3 = Item("Item 3");
Item i4 = Item("Item 4");
i1.setInteractable({i2,i3});
i2.setInteractable({i1,i4});
i3.setInteractable({i1});
This is the method header for the setInteractable method in Item.
void setInteractable(Item i[]);
The interactable items are stored as such:
static Item interactableItems[25];
This doesn't work, the error occurs after the first curly brace. What is the correct way to do this in C++?

Answer 1

You don't want to store objects in your array (otherwise, they are copied), but references to objects.
Change your storage and interface like that:
void setInteractable(Item& i[]);
static Item& interactableItems[25];
I advise to look in google for:
copy constructor
pointer vs object vs reference

Answer 2

C++ doesn't make dynamic lists as easily as you are trying.
To make the dynamic lists you need to first declare a dynamic list:
Item * dlist = new Item[2];
Set them:
dlist[0] = i1;
dlist[1] = i2;
then pass them into your function:
setInteractable(dlist);
Finally you have to remember to clean your memory:
delete [] dlist;
Or... you do this with the standard template library.
std::vector<Item> temp1;
temp1.push_back(i1);
//... other sets
Your function should be:
void setInteractable(std::vector<Item> & list)
{
///
}
The call should be
setInteractable(temp1);

Answer 3

It's a wrong C++ syntax to pass an array initialization like that:
i1.setInteractable({i2,i3}); // error: invalid
In various way you can achieve this. The most straight forward way is to use std::vector.
First declare interactableItems as,
static vector<Item> interactableItems;
Now you don't need setInteractable(), if you make above variable public
Usage:
i1.interactableItems.push_back(Item("Item 2"));
i1.interactableItems.push_back(Item("Item 3"));
If you want to have variable private then you can just put a wrapper and put the push_back inside it.

Answer 4

I would solve the problem like so:
Change the method to work on one object at a time, and loop over them:
void setInteractable(Item &i);
for (int i = 0; i < 25; i++)
for (int j = i + 1; j < 25; j++)
items[i].setInteractable(items[j]);
Much cleaner to deal with. You can store them in a std::vector inside of the Item, and just with those.

Answer 5

I would suggest using one of the STL containers. My implementation will proceed thus:
// Method header for the setInteractable method
#include <vector>
class Item {
private:
// some declarations
public:
void setInteractable(vector<Item &>);
// some other declarations
};
Your implementation should them selectively push Item objects onto vectors before passing them into the function.
Refer to the Cplusplus Reference Site for some more readings on STL containers.