Array of base objects filled with derived objects..

[Exempt]

I was just trying to figure out why this code doesn't work and what would be the best way to go about doing this?

NPC** oEnemies = new Pig*[numPigs];

NPC is the base class and Pig is derived from it. I want to be able to just do something like this in the end.

//Within the logic part of my game loop
for(int i = 0; i < numEnemies; i++)
    oEnemies[i]->AI();

AI() is a virual function from NPC and the Pig class has it's own AI().

Edit:
I meant to mention that just declaring..
NPC* oEnemies = new Pig;
works fine.

[Zhuge]

Why are you using a double pointer? Couldn't you just write
NPC* oEnemies = new Pig[numPigs];?

[Peter87]

Just do

NPC** oEnemies = new NPC*[numPigs];

[vlad from moscow]

I do not see a greate sense in statement

NPC** oEnemies = new Pig*[numPigs];

You should change the code below the following way

//Within the logic part of my game loop
for(int i = 0; i < numEnemies; i++)
    oEnemies[i]->AI();

[Exempt]

that's not the actual code I have and you're right about oEnemies should have the [i] I just didn't notice for this lol... anyway.

Peter NPC is a base class and cannot have an instance of itself.

I will try that Zhuge but the idea is to have pointer to each element of the array not the array itself.

Why can't I have

 NPC** oEnemies = new Pig*[numPigs];
 

...this works fine but doesn't allow me to store all my devired NPC types.

Pig** oPig = new Pig*[numPigs];

Edit: zhuge, I tested what you said out and it is what I thought. It doesn't create pointers to each element of the array only the array itself which isn't what I need.

[cire]

#include <cstdlib>
#include <ctime>
#include <memory>
#include <vector>
#include <iostream>

struct NPC 
{
    virtual void AI() =0 ;
};

struct Pig : public NPC
{
    void AI() { std::cout << "Not by the hair of my chinny chin chin!\n" ; }
};

struct Wolf : public NPC
{
    void AI() { std::cout << "Little pig, little pig!  Let me in!\n" ; }
};


const unsigned numInitialEnemies = 10 ;

int main()
{
    std::srand(std::time(0)) ;

    std::vector<std::unique_ptr<NPC>> enemies ;

    for ( unsigned i=0; i<numInitialEnemies; ++i )
    {
        if ( rand() % 2 )
            enemies.emplace_back(new Pig) ;
        else
            enemies.emplace_back(new Wolf) ;
    }

    for ( unsigned i=0; i<enemies.size(); ++i )
        enemies[i]->AI() ;
}

http://ideone.com/ZJa3jN

[Peter87]

Exempt wrote:

Peter NPC is a base class and cannot have an instance of itself.

new NPC*[numPigs] doesn't create any NPC instances. It creates NPC pointers, which is fine because NPC pointers can point to Pig instances.

[Exempt]

Ah, i see what you mean peter, thanks for clearing it up. Initialize the npc array with new npc's then store my derived pigs or whatever inside. I guess that answers that and i'll need to use a vector list or map to store them the right way i guess like cire has shown.

Thanks for all the replies everyone.