CODEWITHSUNDEEP
c++arrayspointerspolymorphismderived-class
tree-hacker
tree-hacker

Reputation: 5471

C++ fill array with objects derived from array type

In C++ I have an array of pointers to Player objects and want to fill it with Fickle objects where Fickle is a class that is derived from Player. This is because I want a general Player array that I can fill with different objects from different classes that all are derived from the Player class.

How can I do this?

I create an array of pointers to Player objects

Player ** playerArray;

Then initialize the array to a certain size

playerArray = new Player *[numPlayersIn];

But then the following does not work for some reason:

playerArray[i] = new Fickle(0);

How can I fill the playerArray with Fickle objects (Fickel is a class derived from Player) ?

Thanks.

UPDATE:

I get the error message (in Eclipse IDE):

expected ';' before 'Fickle'

I think it might be something to do with the definition of Fickle.

The Fickle.hpp file contains:

#pragma once
#include "player.hpp";

class Fickle: public Player {
public:
    // constructor
    Fickle(int initChoice){
        choice = initChoice;
    }
}

Is this OK or is there a problem with this?

The Player class header file has:

class Player {
private:

public:
    int getChoice();
int choice; // whether 0 or 1
virtual void receive(int otherChoice); // virtual means it can be overridden in subclases
};

The receive method will be overridden in Fickle and other classes derived from the Player class

UPDATE 2:

OK I think the error is actually due to a different part of the code.

Player defines a method receive:

virtual void receive(int otherChoice);

That should be overridden by the subclass Fickle but the definition in Fickle:

void Fickle::receive(int otherChoice) {}

gives the error:

no 'void Fickle::receive(int)' member function declared in class 'Fickle'

But I don't know why this is because receive is defined in the Player class?

Upvotes: 1

Views: 5624

Answers (4)

Yakov Galka
Yakov Galka

Reputation: 72489

It looks like you forgot a semicolon at the end of Fickle class:

class Fickle: public Player {
    // ...
}; // <---- this semicolon

Maybe somewhere else.

UPDATE 2: When you override a virtual function in the derived class you must declare it there too.

Upvotes: 2

MSN
MSN

Reputation: 54614

If it's not compiling correctly, then you probably didn't #include the header that defines Fickle in the same source file you have that code. Usually an error like that means the compiler doesn't know what Fickle is.

Upvotes: 1

Jerry Coffin
Jerry Coffin

Reputation: 490178

While you probably should be using a vector instead, there's no real reason a dynamically allocated array can't work. Here's a bit of working demo code:

#include <iostream>

class Player {
public:
    virtual void show() { std::cout << "Player\n"; }
};

class Fickle : public Player {
public:
    virtual void show() { std::cout << "Fickle\n"; }
};

int main() {
    Player **p = new Player *[2];
    p[0] = new Player;
    p[1] = new Fickle;

    for (int i=0; i<2; i++)
        p[i]->show();

    for (int i=0; i<2; i++)
        delete p[i];
    delete [] p;
    return 0;
}

Upvotes: 5

Mark B
Mark B

Reputation: 96251

Does Fickle have a constructor that accepts an int or pointer type? Is it privately derived from Player? Otherwise it looks like this should work.

Upvotes: 0

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