Passing a pointer object within a function in a header file-CodePudding

I am experincing an issue where the error is: "2061 syntax error: identifier 'Person'

Enemy.h:

#include "person.h"

class Enemy
{
public:
    Enemy(string, string);

    void damage(Person*, Enemy*);
private:
    string name;
    string description;
};

Enemy.cpp:

Enemy::Enemy(string name, string description)
{
    this->name = name;
    this->description = description;
}

void Enemy::damage(Person* person, Enemy* enemy) 
{
    // do something
}

Person.h:

class Person
{
public:
    Person(string, string, int);

private:
    string name;
    string description;
    int health;

};

Person.cpp:

Person::Person(string name, string description, int health)
{
    this->name = name;
    this->description = description;
    this->health = health;
}

This line is causing the 206 error:

void damage(Person*, Enemy*);

Any help would be appreciated, thanks

CodePudding user response：

In Enemy.h you have a declaration void damage(Person*, Enemy*);, and in Enemy.cpp you have a definition void Enemy::doDamage(Person* person, Enemy* enemy). The names damage and doDamage are different.

CodePudding user response：

The code in Enemy.cpp needs to know what the complete Person class looks like in order to access its members. But, since the code in Enemy.h is using only Person* pointers, it just needs to know that the Person class exists but not what it looks like.

There are two ways to approach this:

Make Enemy.h include Person.h, and make Enemy.cpp include Enemy.h, eg:

Enemy.h:

#ifndef Enemy_H
#define Enemy_H

#include <string>
#include "Person.h"

class Enemy
{
public:
    Enemy(std::string, std::string);

    void damage(Person*, Enemy*);
private:
    std::string name;
    std::string description;
};

#endif

Enemy.cpp:

#include "Enemy.h"

Enemy::Enemy(std::string name, std::string description)
{
    this->name = name;
    this->description = description;
}

void Enemy::damage(Person* person, Enemy* enemy) 
{
    // do something
}

Person.h:

#ifndef Person_H
#define Person_H

#include <string>

class Person
{
public:
    Person(std::string, std::string, int);

private:
    std::string name;
    std::string description;
    int health;

};

#endif

Person.cpp:

#include "Person.h"

Person::Person(std::string name, std::string description, int health)
{
    this->name = name;
    this->description = description;
    this->health = health;
}

Alternatively, have Enemy.h forward declare Person, and then include Person.h in Enemy.cpp, eg:

Enemy.h:

#ifndef Enemy_H
#define Enemy_H

#include <string>

class Person;

class Enemy
{
public:
    Enemy(std::string, std::string);

    void damage(Person*, Enemy*);
private:
    std::string name;
    std::string description;
};

#endif

Enemy.cpp:

#include "Enemy.h"
#include "Person.h"

Enemy::Enemy(std::string name, std::string description)
{
    this->name = name;
    this->description = description;
}

void Enemy::damage(Person* person, Enemy* enemy) 
{
    // do something
}

Person.h:

#ifndef Person_H
#define Person_H

#include <string>

class Person
{
public:
    Person(std::string, std::string, int);

private:
    std::string name;
    std::string description;
    int health;

};

#endif

Person.cpp:

#include "Person.h"

Person::Person(std::string name, std::string description, int health)
{
    this->name = name;
    this->description = description;
    this->health = health;
}