How do i change an object through the use of pointers? - c++

Question

#include "Visit.h"
class Patient
{
private:
std::string name;
std::string IC;
List<Visit> *visitList;
List<MC> mcList;
public:
Patient();
Patient(std::string, std::string);
void addVisit(Visit);
List<Visit> *getVisitList();
};
//End of Patient.h
#include "Patient.h"
Patient::Patient()
{
visitList = new List<Visit>();
}
Patient::Patient(std::string ic, std::string n) : name(n), IC(ic)
{
visitList = new List<Visit>();
}
void Patient::addVisit(Visit v)
{
visitList->add(v);
}
List<Visit> * Patient::getVisitList()
{
return visitList;
}
//End of Patient.cpp
class Visit
{
private:
__int64 time;
double cost;
bool xRayStatus = false;
public:
Visit();
Visit(__int64, double);
void addXRay();
bool getXRayStatus();
};
//End of Visit.h
#include "Visit.h"
Visit::Visit() {
}
Visit::Visit(__int64 t, double c) : time(t), cost(c) {
}
void Visit::addXRay()
{
xRayStatus = true;
}
bool Visit::getXRayStatus()
{
return xRayStatus;
};
//End of Visit.cpp
int main()
{
int pos;
Visit v(/*current time, cost*/);
Patient p()
unordered_map<string, Patient> patientMap;
string IC;
getline(cin,IC);
Patient p(IC, "John");
patientMap.insert({IC, p});
Patient *pc;
Visit *vc;
pos = patientMap[IC].getVisitList()->getLength();
pc = &patientMap[IC];
pc->addVisit(v); //Debugger shows patientMap[IC].getVisitList()->getLength() becomes 2
pc->getVisitList()->get(pos).addXRay(); //patientMap[IC].getVistList()->get(0).getXRayStatus() still false
vc = &patientMap[IC].getVisitList()->get(pos);
vc->addXRay(); //patientMap[IC].getVistList()->get(0).getXRayStatus() still false
}
How do i make that getXRayStatus true? It seems odd to me that i can add items into the list but not carry out other functions like vc->addXRay.
vc itself shows true but the change isn't reflected on my map.
pc somehow is able to add Visits and show the change on the map.

Answer 1

In the List<Visit> you are keeping instances of Visits. When you are setting the xRayStatus you are changing the status of the local Visit copy you get from the list, not to the actual object in the list.

Answer 2

In an extended comment conversation, the asker has asked for general redesign help to avoid the problems caused by working with a Visit copy from get(). My redesign suggestions are:
stop using List. Whether you wrote it yourself or got it somewhere else, it's surely more than you need. Use std::vector<> as the collection class of first choice, and change to something else only when you need it.
don't keep pointers to your collections in Patient unless they are likely to be enormous memory hogs. Have vectors as member variables. This will save you having to write a lot of cleanup code.
Stop keeping solid Visit objects in the collections. Use make-shared() or make_unique to get yourself smart pointers to visit objects that are on the heap. Keep these pointers in the vectors and you can deference them to change the real values in the real visits out on the heap
consider adding a date and time or visit number to Visit since at the moment it's not clear to me how you find a specific visit when there is more than one
set properties in things before you put them in collections. Your main knows all about the inside of a Visit (not that I approve of that) but has Patient create an empty one and then jumps through hoops trying to get hold of it and change some of its properties. Why not have Patient set those properties? Or have main() create a Visit, fill in all the properties, and then hand it to Patient saying "here, add this to your collection"? What you're doing now is so much harder than it needs to be.
Finally, find a tutorial, book, or online course that works for you and gets you clear on the difference between objects and pointers, good reasons for using pointers, the need for destructors (you have none at the moment) and for good measure explains the collection classes in std:: and elsewhere. Tutorials and architectural advice are not a good fit for the Q&A mechanism of StackOverflow.