Question

I’d like to use toString with class argument, but for some reason there is an error.
The code is:

Animal.h

#include "Treatment.h"
#include "jdate.h"
#include <vector>

class Animal{
protected:
    int id;
    double weight;
    int yy;
    int mm;
    int dd;
    double accDose;
    char sex;
    vector<Treatment*> treatArray;
public:
    Animal();
    Animal(int newid, double newweight, int yy, int mm, int dd, char newsex, vector<Treatment*> treatArray);
    ~Animal();
};

Treatment.h

#ifndef TRE_H
#define TRE_H
#include <string>
#include <sstream>
#include "jdate.h"
#include "Animal.h"
#include "Cattle.h"
#include "Sheep.h"

class Treatment{
private:
    int id;
    jdate dayTreated;
    double dose;
public:
    Treatment(int id,jdate dayTreated, double dose);
    Treatment();
    ~Treatment();
    string toString(Animal* a);
};
#endif

Treatment.cpp

#include "Treatment.h"

using namespace std;

Treatment::Treatment(int newid,jdate newdayTreated, double newdose){
    id=newid;
    dayTreated = newdayTreated;
    dose = newdose;
}

Treatment::Treatment(){
    id=0;
    dose=0;
}
Treatment::~Treatment(){}

string Treatment::toString(Animal* a)
{
    string aa;
    return aa;
}

toString is in Treatment class. I’m not sure but I think it’s because Animal has
vector treatArray;. Does it actually matter?
Sorry that I cannot put the error messages here, because once I declare toString, for some reason tons of errors occur, such as

Error   1   error C2065: 'Treatment' : undeclared identifier    l:\2011-08\c++\assignment\drug management\drug management\animal.h  30  1   Drug Management

Answer 1

// Animal.h
// #include "Treatment.h"   remove this

class Treatmemt;    // forward declaration

class Animal
{
    ...
};

In your version, Treatment.h and Animal.h include each other. You need to resolve this circular dependency using forward declaration. In .cpp files, include all necessary h-files.