Why can't I update my class properties in C++? - c++

Question

I'm making a Wizard game prototype and I came across an issue:
I created a class called Wizard and a class called Goblin:
class Wizard
{
public:
int damage;
int health;
int stamina;
Wizard(int d, int h, int s)
{
d = damage;
h = health;
s = stamina;
}
float getDamage() { return damage; }
void setDamage(int v) { v = damage; }
float getHealth() { return health; }
void setHealth(int v) { v = health; }
float getStamina() { return stamina; }
void setStamina(float v) { v = stamina; }
};
class Goblin
{
public:
int health;
int damage;
Goblin(int h, int d)
{
h = health;
d = damage;
}
float getHealth() { return health; }
void setHealth(int v) { v = health; }
float getDamage() { return damage; }
void setDamage(int v) { v = damage; }
};
Then, I declared and initialized variables for them:
Wizard wizard(50, 150, 10);
Goblin goblin(150, 25);
Then, I created an attack() function:
void attack(Wizard attacker, Goblin target)
{
if(target.getDamage() > 0.0)
{
attacker.setStamina(attacker.getStamina() - 1);
}
}
So, in the main function, I called attack and printed out the results:
int main()
{
attack(wizard, goblin);
printInfo();
return 0;
}
But this is the result:
> clang++-7 -pthread -std=c++17 -o main main.cpp
> ./main
Wizard Health: 0
Wizard Damage: 0
Wizard Stamina: 0
Goblin Damage: 0
Goblin Health: 0
I also created a printInfo() function:
void printInfo()
{
std::cout << "Wizard Health: " << wizard.getHealth() << std::endl;
std::cout << "Wizard Damage: " << wizard.getDamage() << std::endl;
std::cout << "Wizard Stamina: " << wizard.getStamina() << std::endl;
std::cout << std::endl;
std::cout << "Goblin Damage: " << goblin.getHealth() << std::endl;
std::cout << "Goblin Health: " << goblin.getDamage() << std::endl;
}
Here is the full file if you need it:
#include <iostream>
class Wizard
{
public:
int damage;
int health;
int stamina;
Wizard(int d, int h, int s)
{
d = damage;
h = health;
s = stamina;
}
float getDamage() { return damage; }
void setDamage(int v) { v = damage; }
float getHealth() { return health; }
void setHealth(int v) { v = health; }
float getStamina() { return stamina; }
void setStamina(float v) { v = stamina; }
};
class Goblin
{
public:
int health;
int damage;
Goblin(int h, int d)
{
h = health;
d = damage;
}
float getHealth() { return health; }
void setHealth(int v) { v = health; }
float getDamage() { return damage; }
void setDamage(int v) { v = damage; }
};
Wizard wizard(50, 150, 10);
Goblin goblin(150, 25);
void attack(Wizard attacker, Goblin target);
void printInfo();
int main()
{
attack(wizard, goblin);
printInfo();
return 0;
}
void attack(Wizard attacker, Goblin target)
{
if(target.getDamage() > 0.0)
{
attacker.setStamina(attacker.getStamina() - 1);
}
}
void printInfo()
{
std::cout << "Wizard Health: " << wizard.getHealth() << std::endl;
std::cout << "Wizard Damage: " << wizard.getDamage() << std::endl;
std::cout << "Wizard Stamina: " << wizard.getStamina() << std::endl;
std::cout << std::endl;
std::cout << "Goblin Damage: " << goblin.getHealth() << std::endl;
std::cout << "Goblin Health: " << goblin.getDamage() << std::endl;
}
Sorry if this is very long, but help would be appreciated.

Answer 1

Your attack() function takes parameters by value. As such it modifies a copy of your global variables.
Use references:
void attack(Wizard& attacker, Goblin& target)
{
...
}
PS: see also https://en.cppreference.com/w/cpp/language/constructor to learn about member initializer lists

Answer 2

In your constructors and set* methods you need to assign input parameter values to the member variables of classes. Not vice versa.
#include <iostream>
class Wizard
{
public:
int damage;
int health;
int stamina;
Wizard(int d, int h, int s)
{
damage = d;
health = h;
stamina = s;
}
float getDamage() { return damage; }
void setDamage(int v) { damage = v; }
float getHealth() { return health; }
void setHealth(int v) { health = v; }
float getStamina() { return stamina; }
void setStamina(float v) { stamina = v; }
};
class Goblin
{
public:
int health;
int damage;
Goblin(int h, int d)
{
health = h;
damage = d;
}
float getHealth() { return health; }
void setHealth(int v) { health = v; }
float getDamage() { return damage; }
void setDamage(int v) { damage = v; }
};
Wizard wizard(50, 150, 10);
Goblin goblin(150, 25);
void attack(Wizard attacker, Goblin target);
void printInfo();
int main()
{
attack(wizard, goblin);
printInfo();
return 0;
}
void attack(Wizard attacker, Goblin target)
{
if(target.getDamage() > 0.0)
{
attacker.setStamina(attacker.getStamina() - 1);
}
}
void printInfo()
{
std::cout << "Wizard Health: " << wizard.getHealth() << std::endl;
std::cout << "Wizard Damage: " << wizard.getDamage() << std::endl;
std::cout << "Wizard Stamina: " << wizard.getStamina() << std::endl;
std::cout << std::endl;
std::cout << "Goblin Damage: " << goblin.getHealth() << std::endl;
std::cout << "Goblin Health: " << goblin.getDamage() << std::endl;
}