如何在另一个包含对象的文件中创建一个函数并从 main 调用它

我希望能够制作战斗场景并将其放入函数中，但是每次尝试时，我都必须在不同的头文件中创建对象，然后我无法在main中调用它。为了尝试解决此问题，我在 main 函数中做了循环，但它说调用该方法的对象必须是可修改的。

//main.cpp
int main()
{
    Characters h;//Created using normal constructor
    cout << "Character: n";
    h.setAttack(5);
    h.getAttack();
    h.setDefense(15);
    h.getDefense();
    Hero Me;
    cout << "Hero: n";
    Me.setAttack(10);
    Me.getAttack();
    Me.setHp(5);
    Me.getHp();
    Hero::Hero(1,2,3,4);//Created using overloaded constructor
    Monsters m;
    cout << "Monster: n";
    m.setAttack(20);
    m.getAttack();
    Monsters::Monsters(5,6,7,8);
//Problem is this this loop! i cant access the member functions for my objects.
//And i want to be able to put this in a function and call it from another file!
do
{
    cout << "Attacking!n";
    cout << "Your hp is: " << Me.getHp() << endl;
    cout << "The enemy's hp is: "<< m.getHp << endl;
    cout << "nThe monster has attacked you!n";
    cout << "You received " << m.getStrength() << " damage;" << endl;
    Me.setHp() -= m.getStrength() ;//It compiles an error, saying its not modifiable
    cout << "nYour hp is now: " << Me.getHp() << endl;
    cout << "Enemy hp is: "<< m.getHp << endl;
    cout << "nNow you attacked!nYou have dealt "<< Me.getAttack() << " Damage" <<      endl;
    m.setHp() -= Me.getAttack();
    cout << "Enemy hp is now: " << m.getHp() - Me.getAttack() << endl;
}while ((Me.getHp() >= 0) && (m.getHp() >= 0));
    if ((Me.getHp > 0) && (m.getHp < 0))
 cout <<"Congratulations! You killed the enemy!" << endl;
 else if ((Me.getHp < 0) && (m.getHp > 0))
 cout << "You have died!" << endl;
 cin.sync();
 cin.get();
 return 0;
}

//Here's the rest of my code.
//Hero.h
class Hero:
    public Characters
{
public:
    Hero();
    Hero(int, int, int, int);
    ~Hero(void);
};

//Hero.cpp
int Herolevel;
int HeroHp;
int HeroStrength;
int HeroAttack;
int HeroDefense;
Hero::Hero()
{
    cout << "HOLA! Hero Created using normal constructorn";
}
Hero::Hero(int newHp, int newLevel, int newAttack, int newDef)
{
    cout << "Hero created using Overloaded function!n";
    HeroHp = newHp;
    cout << "Hp is: "<< HeroHp << endl;
    Herolevel = newLevel;
    cout << "level is: " << Herolevel << endl;
    HeroAttack = newAttack;
    cout << "Attack is: " << HeroAttack << endl;
    HeroDefense = newDef;
    cout << "Defense is: " << HeroDefense << endl;
}

Hero::~Hero(void)
{
    cout << "Hero destroyed!n";
}

//Monsters.h
#pragma once
#include "Hero.h"
#include "Characters.h"
class Monsters:
    public Characters //Hero
{
public:
    Monsters(void);
    Monsters(int, int, int, int);
    //Monsters(int);
    ~Monsters(void);
};
//Monsters.cpp
int Monsterlevel;
int MonsterHp;
int MonsterStrength;
int MonsterAttack;
int MonsterDefense;
Monsters::Monsters(void)
{
    "Monster Created";
}
Monsters::Monsters(int newHp, int newLevel, int newAttack, int newDef)
{
    cout << "Monster created using Overloaded function!n";
    MonsterHp = newHp;
    cout << "Hp is: "<< MonsterHp << endl;
    Monsterlevel = newLevel;
    cout << "level is: " << Monsterlevel << endl;
    MonsterAttack = newAttack;
    cout << "Attack is: " << MonsterAttack << endl;
    MonsterDefense = newDef;
    cout << "Defense is: " << MonsterDefense << endl;
}
Monsters::~Monsters(void)
{
    cout << "nMonster Destroyed";
}

//Characters.h
#pragma once
class Characters
{
private:
    int level;
    int Hp;
    int Strength;
    int Attack;
    int Defense;
public:
    Characters(void);
    Characters(int);
    Characters(int, int, int, int);
    ~Characters(void);

    int getAttack();
    int getDefense();
    int getStrength();
    int getHp();
    int getLevel();
    void setAttack(int);
    void setDefense(int);
    void setStrength(int);
    void setHp(int);
    void setlevel(int);
};

//Characters.cpp
Characters::Characters(void)
{
    cout << "nCharacter has been created!n";
}
Characters::Characters(int random)//How can i make this work?
{
    cout << "Level " << level << " character created with: n";
    /*srand ((unsigned)time(0));
    random = rand() % 10 + 1;
    setlevel(int random);*/
    level = random;
}
Characters::~Characters(void)
{
    cout << "Character has been destroyed!n";
}
void Characters::setAttack(int att)//get Character left over hp
    {
        Attack = att;
    }
void Characters::setDefense(int def)//get Character left over hp
    {
        Defense = def;
    }
void Characters::setStrength(int str)//get Character left over hp
    {
        Strength = str;
    }
void Characters::setHp(int damage)//get Character left over hp
    {
        Hp -= damage;
    }
void Characters::setlevel(int lvl)//get Character left over hp
    {
        level = lvl;
    }

int Characters::getAttack()
{
    cout << "Your attack is: " << Attack << endl;
    return Attack;
}
int Characters::getDefense()
{
    cout << "Your defense is: " << Defense << endl;
    return Defense;
}
int Characters::getStrength()
{
    cout << "Your strength is: " << Strength << endl;
    return Strength;
}
int Characters::getHp()
{
    cout << "Your hp is: " << Hp << endl;
    return Hp;
}
int Characters::getLevel()
{
    cout << "Your level is: " << level << endl;
    return level;
}