C++ Vending Machine program with classes c++ - c++

Question

I am trying to build a vending machine program with 3 different classes but I am stuck on the second portion of it. Basically the first class is the snack class, which takes 3 parameters (calories, name and price.) However, the second class VendSlot, should have two members, a snack (which I presume to be the object from the first files) and the quantity of snacks. I am really struggling to understand how to process the snack object within the second class though. How exactly do I pass the first snack object into my VendSlot class so that I can increase/decrease the amount in my storage in VendSlot and then let the user buy it when I reach the third item? I can't use pointers yet but can pass by reference and I am wondering if this is an effective way? The third class will be a vending machine that will have vendSlots and will take money to buy the items. Thank you for the help and let me know if you need clarification on the project!
This is my Snack header file
#ifndef SNACK_CPP
#include <string>
using std::string;
class Snack
{
private:
string nameOfSnack;
double snackPrice;
int numOfCalories;
public:
Snack(); //default constructor
Snack(string, double, int); //overload constructor
~Snack(); //destructor
//Accessor functions
string getNameOfSnack(); //returns name of snack
double getSnackPrice(); //returns the price of the snack
int getNumOfCalories(); //returns number of calories of snack
};
#endif // !SNACK_CPP
This is my snack.cpp file with constructors
#include "Snack.hpp"
#include <iostream>
#include <string>
using std::endl;
using std::string;
using std::cout;
using std::cin;
Snack::Snack() //default constructor
{
nameOfSnack = "bottled water";
snackPrice = 1.75;
numOfCalories = 0;
}
Snack::Snack(string name, double price, int cals)
{
nameOfSnack = name;
snackPrice = price;
numOfCalories = cals;
}
Snack::~Snack()
{
}
string Snack::getNameOfSnack()
{
return nameOfSnack;
}
double Snack::getSnackPrice()
{
return snackPrice;
}
int Snack::getNumOfCalories()
{
return numOfCalories;
}
Here is my VendSlot header file
#ifndef VENDSLOT_CPP
#include "Snack.h"
#include <string>
class VendSlot
{
public:
VendSlot(); //default constructor
VendSlot(string, double); //overload constructor
string getSnack(); //get snack name
int getAmount(); //get amount of snacks available
void decrementAmount(int); //function to decrease storage in vending machine by 1.
Snack snack; //passes snack object? I am confused what this should be.
~VendSlot(); //destructor
private:
double numOfSnacks; // number of snacks
};
#endif // !VENDSLOT_CPP
And here is my VendSlot.cpp file which I am struggling with
#include "VendSlot.h"
#include "Snack.h"
#include <iostream>
#include <string>
using std::cout;
using std::cin;
using std::endl;
using std::string;
VendSlot::VendSlot()
{
snack;
numOfSnacks = 5;
}
VendSlot::VendSlot(string Snack, double Quantity)
{
snack = Snack;
numOfSnacks = Quantity;
}
int VendSlot::getAmount()
{
return numOfSnacks;
}
string VendSlot::getSnack()
{
return snack;
}
VendSlot::~VendSlot()
{
}

Answer 1

I'm not sure if this is the point of your program or assignment. I'm answering your question of how does the Snack class get its constructor params when it is contained within VendSlot class.
The members contained in another class get their constructor parameters from the initialization list.
Here is an example for your case of how it could be done:
Snack::Snack(string name, double price, int cals) :
nameOfSnack(name),
snackPrice(price),
numOfCalories(cals)
{
}
VendSlot::VendSlot(Snack& snack, int quantity) :
snack(snack),
numOfSnacks(quantity)
{
}
Also, note using a reference is what would normally be used when passing in an entire class or struct. This also means the default Snack copy constructor provided by the compiler will be used unless you implement one yourself. If the class only has simple native types it should work, but to be safe you should implement it yourself.
The member quantity would seem to be best be an int type as you wouldn't have fractions of a snack being sold.
Here's the assignment operator and copy constructor defined as you'll need it.
Snack& Snack::operator=(const Snack& snack)
{
this->nameOfSnack = snack.name;
this->snackPrice = snack.price;
this->numOfCalories = snack.cals;
}
Snack::Snack(const Snack& snack)
{
*this = snack;
}

Answer 2

When you work with classes in C++, imagine them as variables that contain variables. So use them the same way as you use variables.
When you call an instance of a class (or "declare the variables") the constructor is called. There are two ways on doing this. With or without parameters:
Snack A("Chocolate", 12.5, 199);//This will call the constructor with parameters
Snack B;//This will call the constructor without parameters
So now we have two objects of the same class. To use the memebers of the objects we just use a period.
cout << A.getNameOfSnack() << endl;//Output: Chocolate
cout << B.getNameOfSnack() << endl;//Output: bottled water
Also, keep in mind that we can access to the public members only.
Moving on, creating an instace of a class as a member of other class is not different.
class VendSlot {
public:
Snack snack;
int numOfSnacks;
VendSlot();
VendSlot(string, double);
~VendSlot();
};
VendSlot::VendSlot() {
snack = Snack();//Call the constructor to create the object
numOfSnacks = 5;
}
VendSlot::VendSlot(string nameSnack, double Quantity) {//Notice that I changed the name of the first parameter
snack = Snack(nameSnack, 0, 0);//Call the constructor to create the object
numOfSnacks = Quantity;
}
First, you need to be sure that you are not using the name of the class as the name of a variable (that will give you errors, so be careful with that). Now, since the only data you recive in the VendSlot constructor is the name of the snack, there is no more information to send as parameter to the constructor of Snack. You can either add more parameters on the VendSlot constructor or put default values.
Since the variables nameOfSnack, snackPrice and numOfCalories are private members of their class we can't change their values from outside the class Snack.
Within the class VendSlot (or where you create the instance of the class) you can only call the functions getNameOfSnack, getSnackPrice and getNumOfCalories, which are public members of Snack.
So, implying that the function VendSlot::getSnack returns the name of the snack, the function will be as following.
string VendSlot::getSnack() {
return snack.getNameOfSnack();
}
I hope this answers your question.