How to allow user input in objects and classes? - c++

Question

Consider the following code:
#include <iostream>
using namespace std;
class inventory
{
public:
~inventory()
{
cout << "This Object is being destroyed" << endl;
}
inventory()
{
itemNumber = 0;
quantity= 0;
cost= 0;
}
inventory(int itemNumber1, int quantity1, double cost1)
{
setItemNumber(itemNumber1);
setQuantity(quantity1);
setCost(cost1);
}
void setItemNumber(int itemNumber2)
{
itemNumber=itemNumber2;
}
bool setQuantity(int quantity2)
{
bool userTrue = true;
bool userFalse = false;
if (quantity2 < 0)
{
quantity = 0;
return userFalse;
}
else
{
quantity= quantity2;
return userTrue;
}
}
bool setCost(double cost2)
{
bool userTrue = true;
bool userFalse = false;
if (cost2 < 0.0)
{
cost = 0.0;
return userFalse;
}
else
{
cost= cost2;
return userTrue;
}
}
double getTotalCost(int quantity, double cost)
{
int total;
total = (quantity * cost);
return total;
}
private:
int itemNumber;
int quantity;
double cost;
};
int main()
{
int itemNumberInput;
int quantityInput;
double costInput;
cout << "Enter the Item Number: " << endl;
cin >> itemNumberInput;
cout << "Enter the Quantity : " << endl;
cin >> quantityInput;
cout << "Enter the Cost : " << endl;
cin >> costInput;
inventory *pointerA, *pointerB;
pointerA = new inventory;
pointerB = new inventory(inventory(itemNumberInput , quantityInput , costInput));
inventory firstObject(itemNumberInput,quantityInput,costInput);
int itemNumberInput1;
int quantityInput1;
double costInput1;
cout << "Enter the Item Number: " << endl;
cin >> itemNumberInput1;
cout << "Enter the Quantity : " << endl;
cin >> quantityInput1;
cout << "Enter the Cost : " << endl;
cin >> costInput1;
inventory secondObject(itemNumberInput1,quantityInput1,costInput1); // not sure if thats correct
cout << secondObject.setItemNumber(); // not working
cout << secondObject.setQuantity(); // not working
cout << secondObject.setCost(); // not working
return 0;
}
The code above is supposed to take three user inputs, and send them to the classes, and the classes will do their job.
I'm currently stuck at the end where its giving me an error.
In the second object where the values are asked from the user, it should send these values to the classes.
Instead, I'm getting the error.
How can I resolve this problem?

Answer 1

Here is the fixed code:-
#include <iostream>
using namespace std;
class inventory
{
public:
~inventory()
{
cout << "This Object is being destroyed" << endl;
}
inventory()
{
itemNumber = 0;
quantity= 0;
cost= 0;
}
inventory(int itemNumber, int quantity, double cost)
{
this->itemNumber = itemNumber;
this->quantity = quantity;
this->cost = cost;
}
void setItemNumber(int itemNumber)
{
this->itemNumber=itemNumber;
}
bool setQuantity(int quantity)
{
bool userTrue = true;
bool userFalse = false;
if (quantity < 0)
{
this->quantity = 0;
return userFalse;
}
else
{
this->quantity= quantity;
return userTrue;
}
}
bool setCost(double cost)
{
bool userTrue = true;
bool userFalse = false;
if (cost < 0.0)
{
this->cost = 0.0;
return userFalse;
}
else
{
this->cost= cost;
return userTrue;
}
}
double getTotalCost(int quantity, double cost)
{
return quantity * cost;
}
private:
int itemNumber;
int quantity;
double cost;
};
int main()
{
int itemNumberInput;
int quantityInput;
double costInput;
cout << "Enter the Item Number: " << endl;
cin >> itemNumberInput;
cout << "Enter the Quantity : " << endl;
cin >> quantityInput;
cout << "Enter the Cost : " << endl;
cin >> costInput;
inventory *pointerA, *pointerB;
pointerA = new inventory;
pointerB = new inventory(inventory(itemNumberInput , quantityInput , costInput));
inventory firstObject(itemNumberInput,quantityInput,costInput);
int itemNumberInput1;
int quantityInput1;
double costInput1;
cout << "Enter the Item Number: " << endl;
cin >> itemNumberInput1;
cout << "Enter the Quantity : " << endl;
cin >> quantityInput1;
cout << "Enter the Cost : " << endl;
cin >> costInput1;
// The below line is correct
// inventory secondObject(itemNumberInput1,quantityInput1,costInput1);
//Alternatively
inventory secondObject;
secondObject.setItemNumber(itemNumberInput1);
secondObject.setQuantity(quantityInput1);
secondObject.setCost(costInput1);
delete pointerA; // delete dynamically allocated memory to avoid memory leak
delete pointerB;
return 0;
}

Answer 2

Well you've constructed 'secondObject' object using the 3-arg constructor, using the user-entered values as parameters. Therefore, the member variables of this object are being set via the constructor and using the 'set' methods aren't really necessary. In your case, the set methods would be useful if you wanted to change the values later on. For example, lets pretend the user enters 10, 10, and 2.5 for the values. You're then using the constructor to construct the object with those values. The only difference is you're placing those values into variables first. But it works the same way. If you wanted to change the value of quantity later on, you could do secondObject.setQuantity(2); And the quantity for that object is now set to 2. The reason why your calls to .set aren't working is because you need to pass in parameters to these methods i.e. the value you want to set it to.
In regard to the destructor method being printed, objects are destroyed when they go out of scope so that the memory is released. Normally, nothing would happen in terms of output- the object would just go out of scope and the compiler would free up the memory and go about its' business. However, you've coded a custom destructor that prints out 'The Object is being destroyed', which it is at the end of the main. It's likely your constructor is working fine, I'm just not sure what you expect to be happening. I'd also suggest you read up on memory leaks in C++, especially in regard to the 'new' keyword.