Array of pointers to objects and inherited objects - c++

Question

I am trying to make a program which creates an array of pointers to objects, including inherited objects.
The error I'm getting is on the first bracket ( of the cSClass eg SArray[2] = new cSClass(...); (Last line at the bottom of all the code). The error says "no instance of constructor cSClass::cSClass matches the argument list"
Thank you
All the code is below:
The code for the header of the superclass is:
class sClass;
class sClass {
protected:
std::string name;
int yearBuilt;
public:
// Constructor
sClass(string n = "s1", int yb = 2000) {
name = n;
yearBuilt = yb;
}
// Mutator functions
void setName(string);
void setYearBuilt(int);
// Accessor functions
string getName() {
return name;
}
int getYearBuilt() {
return yearBuilt;
}
// Functions
void getInfo();
};
main class of the superclass:
#include "sClass.h"
using namespace std;
// Mutators
void sClass::setName(string n) {
name = n;
}
void sClass::setYearBuilt(int yb) {
yearBuilt = yb;
}
// Print function
void sClass::getInfo() {
cout << "Name: " << name << endl;
cout << "Year Built: " << yearBuilt << endl;
}
Code for the subclass header:
#include "sClass.h"
class cSClass : public sClass {
protected:
int maxPassengers;
public:
// Constructor
cSClass(int mp = 2000) : sClass() {
maxPassengers = mp;
}
// Mutator functions
void setMaxPassengers(int);
// Accessor functions
int getMaxPassengers() {
return maxPassengers;
}
// Functions
void getInfo() {
}
};
Code for the subclass class:
#include "cSClass.h"
// Mutators
void cSClass::setMaxPassengers(int mp) {
maxPassengers = mp;
}
// Print function
void cSClass::getInfo() {
cout << "Name: " << name << endl;
cout << "Maximum Passengers: " << maxPassengers << endl;
}
And lastly this is the main program code in which i am getting errors where i am trying to fill the array:
#include "sClass.h"
#include "cSClass.h"
int main() {
sClass *SArray[6];
SArray[0] = new sClass(...);
SArray[1] = new sClass(...);
SArray[2] = new cSClass(...);
SArray[3] = new cSClass(...);
}
Edit: Error is at the top, and the arguments I'm passing are
SArray[2] = new cSClass("RMS Queen Mary 2", 2003, 2700);

Answer 1

The constructor needed for this to work is missing:
SArray[2] = new cSClass("RMS Queen Mary 2", 2003, 2700);
It could look like this
class cSClass : public sClass {
cSClass(const std::string& name, int yb, int mp) :
sClass(name, yb),
maxPassengers{mp}
{}
//...
}
You also have some other problems:
You have a non-virtual destructor in the base class. When you delete your objects through a non-virtual base class pointer, only the base class destructor will be called. To fix that, add this to sClass:
virtual ~sClass() = default;
Two definitions of cSClass::getInfo(). Settle for only declaring the function in the class definition and leave the definition of the member function in the .cpp file as-is.
Memory leaks since you don't delete what you've newed. To avoid that problem, it's better to use smart pointers that will delete the object when it goes out of scope, like it will in case an exception is thrown (that you catch). Example:
#include <memory>
//...
std::unique_ptr<sClass> SArray[6]; // or std::array<std::unique_ptr<sClass>, 6> sArray;
SArray[2] = std::make_unique<sClass>();
SArray[2] = std::make_unique<cSClass>("RMS Queen Mary 2", 2003, 2700);
Note: If you instead want a dynamic amount of sClass pointers, use a std::vector:
#include <vector>
//...
std::vector<std::unique_ptr<sClass>> SArray;
SArray.push_back(std::make_unique<sClass>());
SArray.push_back(std::make_unique<sClass>());
SArray.push_back(std::make_unique<cSClass>("RMS Queen Mary 2", 2003, 2700));
SArray.push_back(std::make_unique<cSClass>("RMS Queen Mary 2", 2003, 2700));

Answer 2

There are two fundamental errors in your code!
First, you have provided two definitions for the getInfo member function of the cSClass. If you want to keep the second (out-of-body) definition, then you need to remove the definition part of the (in-body) declaration. So, replace:
// Functions
void getInfo() { /// Note: adding the { } provides a function DEFINITION
}
with this:
// Functions
void getInfo(); // No body provided, so it's JUST a declaration (defined elsewhere)
Then, the calls you make to your constructors cannot have the ... in the argument list (though I'm not sure what you are trying to achieve with this). Simply provide empty argument lists:
SArray[0] = new sClass();
SArray[1] = new sClass();
SArray[2] = new cSClass();
SArray[3] = new cSClass();
or, as there is no argument, you can invoke the 'default' constructor by omitting the argument lists completely:
SArray[0] = new sClass;
SArray[1] = new sClass;
SArray[2] = new cSClass;
SArray[3] = new cSClass;
Also, for completeness, remember to free the memory for the objects you created with new, when you're done with them:
delete SArray[0];
delete SArray[1];
delete SArray[2];
delete SArray[3];
Feel free to ask for further clarification and/or explanation.