Virtual function don't work - c++

Question

This code isn't compiled. All problems in virtual function attack() in basic class.
It hasn't got acces to massive in class Team. I was trying do theese classes friend.But it do not work whatever. Also I've done function ptr but it don't work.
Virtual function don't work in inherited classes too. Visual studio 2015 shows errors:
C2228, C2227, C2027.
Please help.
class Team;
class Unit
{
protected:
int hp;
int dmg;
int doodge;
public:
Unit(int hp, int dmg, int doodge): hp(hp), dmg(dmg), doodge(doodge){}
int GetHP()
{
return hp;
}
void SetHP(int hp)
{
this->hp = hp;
}
virtual void attack(Team &T)
{
int id = rand() % 3;
for (int i = 0; i < 3; i++)
if (typeid(*this) == typeid(T.arr[i]))
{
id = i;
break;
}
if (T.arr[id] <= 0)
return;
else
T.arr[id]->SetHP(T.arr[id]->GetHP() - this->dmg);
}
};
class Swordsman:public Unit
{
public:
Swordsman():Unit(15,5,60){}
//virtual void attack(Team & T)override
//{
// int id = rand() % 3;
// for (int i = 0; i < 3; i++)
// if (typeid(Swordsman) == typeid())
// {
// id = i;
// break;
// }
// if (*T.arr[id]->GetHP <= 0)
// return;
// else
// *T.arr[id]->SetHP(T.arr[id]->GetHP() - dmg);
//}
};
class Archer :public Unit
{
public:
Archer() :Unit(12, 4, 40) {}
//virtual void attack(Team & T)override
//{
// int id = rand() % 3;
// for (int i = 0; i < 3; i++)
// if (typeid(Archer) == typeid())
// {
// id = i;
// break;
// }
// if (*T.arr[id]->GetHP <= 0)
// return;
// else
// *T.arr[id]->SetHP(T.arr[id]->GetHP() - dmg);
//}
};
class Mage :public Unit
{
public:
Mage() :Unit(8, 10, 30) {}
/*virtual void attack(Team & T)override
{
int id = rand() % 3;
for (int i = 0; i < 3; i++)
if (typeid(*this) == typeid())
{
id = i;
break;
}*/
};
class Team
{
static short counter;
string name;
Unit* arr[3];
public:
Team()
{
name = "Team " + counter++;
for (int i = 0; i < 3; i++)
{
int selecter = rand() % 3;
switch (selecter)
{
case 0:
arr[i] = new Swordsman();
break;
case 1:
arr[i] = new Archer();
break;
case 2:
arr[i] = new Mage();
break;
}
}
}
~Team()
{
delete[]arr;
}
Unit * ptr(int id)
{
return arr[id];
}
bool check()
{
bool res = false;
for (int i = 0; i < 3; i++)
if (arr[i]->GetHP() > 0)
res = true;
return res;
}
void print()
{
cout << endl << "\t\t" << name << endl << endl;
cout << "\t" << typeid(*arr[0]).name() << endl;
cout << "\t" << typeid(*arr[1]).name() << endl;
cout << "\t" << typeid(*arr[2]).name() << endl;
}
friend class Unit;
};
short Team::counter = 0;
class Game
{
Team A, B;
public:
int Play()
{
while (true)
{
A.ptr(1)->attack(B);
if (A.check())
return 1;
else if (B.check())
return 2;
}
}
};
int main()
{
return 0;
}

Answer 1

Omitting anything irrelevant:
class Team;
class Unit
{
public:
virtual void attack(Team &T)
{
if(typeid(*this) == typeid(T.arr[i]))
// ^^^
{ }
}
};
You are accessing a member of class Team, but at the time given, you only have provided the declaration of Team... Side note: this is not specific to virtual functions, but would occur with any code you write.
Your problem now is that function implementations of both classes Team as well as Unit rely on the complete definition of the other class. So only solution to the problem is to implement one of the functions outside the class, e. g.:
class Team;
class Unit
{
public:
// requires Team, so only declared, not implemented!
virtual void attack(Team &T);
// ^
};
class Team
{
// complete definition!
};
void Unit::attack(Team& t)
{
// now implementation of...
}
Another minor problem is that arr member is private. Well, you provided a getter already (ptr), so use it (and give it a better name...).
If you want to go further towards a clean design, split your units and the team into different compilation units, each coming with a header and a source file:
unit.h:
class Team;
class Unit
{
// private members
public:
// only declarations as above, including constructor/destructor
// by the way: you are lacking a virtual destructor!!!
virtual ~Unit();
};
unit.cpp:
#include "unit.h"
#include "team.h" // fetch the definition of Team!
Unit(/*...*/) { }
Unit::~Unit() { }
// function definitions as shown above...
You would do the same for Team and even your Unit derived classes as well as the Game class. Be aware, though, that you need the complete class definition available if you want to inherit, so you need to include unit.h already int the headers:
archer.h:
#include "unit.h"
class Archer : public Unit
{
// again, only function declarations...
// as base class has already a virtual destructor, own destructor
// gets virtual implicitly (even the default one), so if you do
// not need it, you do not have to define it...
};
archer.cpp:
#include "archer.h"
// and whatever else needed, solely, unit.h already comes with archer.h
// implementations...