What's the Difference?

[dark ninjuh]

I can not seem to grasp the difference between creating objects derived from structures/classes and creating pointers that can use the functions derived from structures/classes.

what i mean is, why do this

#include <iostream>
//type players health, display players health
using namespace std;
class player{
private:
    int health;
public:
    void displayhealth(){
    cout << health;
    }
    void sethealth(){
    cin >> health;
    }

};
int main()
{
//***************************************
    player one;
    player * thing; //this Section
    thing = &one;
    thing->sethealth();
    thing->displayhealth();
//********************************
    return 0;
}

when you can do this

#include <iostream>
//type players health, display players health
using namespace std;
class player{
private:
    int health;
public:
    void displayhealth(){
    cout << health;
    }
    void sethealth(){
    cin >> health;
    }

};
int main()
{
//************************************
    player one;
    one.sethealth(); //compared to this
    one.displayhealth();
//************************************
    return 0;
}

[TwilightSpectre]

Its to do with polymorphism, where the types aren't exactly the same:

#include <iostream>

struct A {
    virtual void doSomething() {
        std::cout << "A::doSomething\n";
    }
};

struct B : A {
    virtual void doSomething() override {
        std::cout << "B::doSomething\n";
    }
};

void func(A* a) {
    a->doSomething();
}

int main() {
    A a;
    func(&a); // prints A::doSomething

    B b;
    func(&b); // prints B::doSomething

    return 0;
}

[MiiNiPaa]

Also [smart]pointers are unavoidable (however they will probably be encapsulated inside classes) if you need to create very large objects:

struct big
{
    char a[50 * 1024 * 1024];
};

int main()
{
//    big x;
//           Segmentation fault
    big y = new big; // OK
}

[megatron 0]

Another reason for using a pointer would be for something like this:

class Player
{
private: int x, y;
public:
    void GoNorth(int offset) { y += offset; }
    /* Other functions */
    int GetX() { return x; }
    int GetY() { return y; }
};

class Map
{
private:
    Player* MapPlayer;
public:
    Map(Player& p): MapPlayer(p) {} // If Player.GoNorth() is called, player on map auto updates it's coordinates
};