So I have the main parent class called item and that class has 2 child classes called book and periodical. The ideas behind what I am trying to do is have a polymorphic array or a polymorphic vector that would be able to do something like this: Now the example is in C# (but I want to do it in C )

    item [ ] items = new items [100]; 
    items[0] = new book(); 
    items[1] = new periodical();
    for (int i = 0; i < items.size; i   ) {
            items[i].read();
    }

Like I said, the small example code is in C# but I want to do this in C but I am not sure how to go about going it. I wanted to use arrays but I'm my research, I haven't found a clear way of how to accomplish this. I also thought if vectors were possible to use or this but I was not sure about that either.

CodePudding user response：

Here is an example (if you have questions let me know):

#include <iostream>
#include <memory>
#include <vector>

class Item
{
public:
    virtual ~Item() = default; // base classes with virtual methods must have a virtual destructor
    virtual void read() = 0;
};

class Book final :
    public Item
{
public:
    void read() override
    {
        std::cout << "book read\n";
    }
};

class Periodical final :
    public Item
{
public:
    void read() override
    {
        std::cout << "periodical read\n";
    }
};

int main()
{
    std::vector<std::unique_ptr<Item>> items;

    // use emplace_back for temporaries
    items.emplace_back(std::make_unique<Book>());
    items.emplace_back(std::make_unique<Periodical>());

    // range based for loop over unique_pointers in items
    // use const& so item cannot be modified and & to avoid copy of unique_ptr (unique_ptr doesn't have a copy constructor)
    for (const auto& item : items)
    {
        item->read();
    }

    return 0;

}