Beginner to class problem

[jjordan33]

Hi,

I'm a student, and my c++ class has an online homework called zybooks and it's a mixture of participation and some challenges. We've begun classes, and it's 98% a self learning course, and I'm having trouble understanding what's going on in the code.

It's a snippet of code pre-coded by zybooks and I have to add in a piece of code to make it work.

  #include <iostream>
#include <string>
#include <vector>
using namespace std;

class BaseItem {
public:
   void SetLastName(string providedName) {
      lastName = providedName;
   };

// i can only edit from here...
   // FIXME: Define PrintItem() member function ....  // this is my snippet. 
void PrintItem(){
   cout << "Last name: " << " " << lastName << endl;
   
}
   // to here. I can't touch any of the rest of the code.

protected:
   string lastName;
};

class DerivedItem : public BaseItem {
public:
   void SetFirstName(string providedName) {
      firstName = providedName;
   };

   void PrintItem() {
      cout << "First and last name: ";
      cout << firstName << " " << lastName << endl;
   };

private:
   string firstName;
};

int main() {
   BaseItem*    baseItemPtr    = nullptr;
   DerivedItem* derivedItemPtr = nullptr;
   vector<BaseItem*> itemList;
   unsigned int i;

   baseItemPtr = new BaseItem();
   baseItemPtr->SetLastName("Smith");

   derivedItemPtr = new DerivedItem();
   derivedItemPtr->SetLastName("Jones");
   derivedItemPtr->SetFirstName("Bill");

   itemList.push_back(baseItemPtr);
   itemList.push_back(derivedItemPtr);

   for (i = 0; i < itemList.size(); ++i) {
      itemList.at(i)->PrintItem();
   }

   return 0;
}

My code inserts this into console stream:
Last name: Smith
Last name: Jones

It needs to insert this:
Last name: Smith
First and last name: Bill Jones

I know there's something to do with there being two void print functions being called, and I'm sure the problem lies therein, but I am so lost on classes right now.

**edit** it shouldn't be a void should it?

[Duthomhas]

Void has nothing to do with it.

The base function needs to be declared virtual:

  virtual void PrintItem()
  {
    cout << "Last name: " << " " << lastName << endl;
  }

The derived class’s override should technically also have the virtual keyword...

Hope this helps.

[jjordan33]

It certainly passed all tests, so thank you for that.

A couple questions so I understand though:

Is virtual something that should be used for classes in general?

So, could I use lastName in any function because it's protected or because it's just part of a class?

[AbstractionAnon]

Is virtual something that should be used for classes in general?

virtual is used on functions in base classes where you want to overload the same function in the derived class.

could I use lastName in any function because it's protected

You can use lastname is any class derived from BaseItem.