C : Array of differents types of objects (access to the methods of the child class)-CodePudding

I have created an array of Position which is a parent class of several classes : Player, Item, Mob, and Map.

I want to create an array of several types of objects in my Position array (dynamically created object) and then want to use the methods of my objects which are unique.

I can't use the virtual type because I would have to write the methods of all my classes and it would be incoherent.

So I ask you to try to solve this problem.

Map.h :

...
static constexpr int mapColonne{14};
static constexpr int mapLigne{6};
Position *positionObject[mapLigne][mapColonne];
...

Map.cpp :

...
positionObject[i][j] = new Player("Player1");
positionObject[i][j]->infoPlayer();
...

Error: class "Position" has no member "infoPlayer

CodePudding user response：

You have following options, depending on what do you want to happen if the element doesn't contain the type you think it does:

static_cast<Player *>(positionObject[i][j])->infoPlayer(); - undefined behavior on type mismatch.
dynamic_cast<Player *>(positionObject[i][j])->infoPlayer(); - cast returns null on type mismatch, which you can check for. If you don't check for null, calling a method on a null pointer might crash.
dynamic_cast<Player &>(*positionObject[i][j]).infoPlayer(); - exception on type mismatch.

I would use:

(3) if I think I know the right type.
(1) if I'm absolutely certain I know the type.
(2) if I want to check the type first, and do something else if it doesn't match.

dynamic_cast is often a sign of bad design. I see no reason to use it here. All your classes should have common methods (declared in base class), such as draw(), update(), etc, which you would call for every object on the board.