Метод, ошибка this

#include <iostream>
#include <string>
#include <fstream>
 
class SickKoala
{
private:
    std::string name;
public:
    std::string getName();
    SickKoala(const std::string &);
    ~SickKoala();
    void poke();
    bool takeDrug(const std::string &);
    void overDrive(std::string &);
};
 
std::string SickKoala::getName()
{
    return this->name;
}
 
SickKoala::SickKoala(const std::string & s)
{
    name = s;
}
 
SickKoala::~SickKoala()
{
    std::cout << "Mr. " << name <<": Kreogg!!  I am healthy!!\n";
}
 
void SickKoala::poke()
{
    std::cout << "Mr. "<< name <<": Gooeeeeerrk !! :’(\n";
}
 
bool SickKoala::takeDrug(const std::string & s)
{
    if(!stricmp(s.c_str(), "mars"))
    {
        std::cout << "Mr. " << name <<": Mars, and it Kreog !\n";
        return true;
    }
    else if(s == "Buronzand")
    {
        std::cout << "Мr. " << name << ": I'm so weak !\n";
        return true;
    }
    std::cout << "Мr. " << name << ": Goerk !\n";
    return false;
}
 
void SickKoala::overDrive(std::string & s)
{
    size_t  found = s.find("Kreog !");
    do
    {
        s.replace(int(found), 7, "1337 !");
        found = s.find("Kreog !",found+1);
    }while(found != std::string::npos);
    std::cout << "Mr. " << name << ": " << s << std::endl;
}
 
class Sister
{
private:
    int id;
    std::string status;
    unsigned int callCount;
public:
    Sister(const int);
    ~Sister();
    void giveDrug(const std::string &, const SickKoala*);
    std::string readReport(const std::string &);
    void timeCheck();
};
 
Sister::Sister(const int id)
{
    this->id = id;
    this->callCount = 0;
}
 
Sister::~Sister()
{
    std::cout << "Nurse " << this->id << " : At last, a little leasure time!\n";
}
 
void Sister::giveDrug(const std::string & s, const SickKoala* p)
{
 
}
 
std::string readReport(const std::string & s)
{
    std::ifstream file(s);
    std::string pilos;
    if(!file)
    {
        std::cout << "Cant open file\n";
        return pilos;
    }
    std::getline(file, pilos);
    if(pilos == "")
    {
        std::cout << "File is empty\n";
        return pilos;
    }
    else
        std::cout << "Nurse " << this->id << " : Kreog ! I have to give " << pilos << " to Mr. " << SickKoala::getName() << " !\n"; \\ тут не работате
    return pilos;
}
 
void Sister::timeCheck()
{
    if(this->callCount == 0)
    {
        std::cout << "Nurse " << this->id << " : I get to work!\n";
        this->callCount = 1;
    }
    else
    {
        std::cout << "Nurse " << this->id << " : I get back to my eucalyptus forest!\n";
        this->callCount = 0;
    }
}
 
int main()
{
    SickKoala koala("Shorty");
    std::string s = "MARS"; 
    koala.takeDrug(s);
}

std::string Sister::readReport(const std::string & s)
{
    std::ifstream file(s);
    std::string pilos;
    if(!file)
    {
        std::cout << "Cant open file\n";
        return pilos;
    }
    std::getline(file, pilos);
    if(pilos == "")
    {
        std::cout << "File is empty\n";
        return pilos;
    }
    else
        std::cout << "Nurse " << this->id << " : Kreog ! I have to give " << pilos << " to Mr. " << SickKoala::getName() << " !\n";
    return pilos;
}

std::string Sister::readReport(const std::string & s, SickKoala* p)
{
    std::ifstream file(s);
    std::string pilos;
    if(!file)
    {
        std::cout << "Cant open file\n";
        return pilos;
    }
    std::getline(file, pilos);
    if(pilos == "")
    {
        std::cout << "File is empty\n";
        return pilos;
    }
    else
        std::cout << "Nurse " << this->id << " : Kreog ! I have to give " << pilos << " to Mr. " << (*p).getName() << " !\n";
    return pilos;
}