Question

Is there any practical way to get objects to work with maps? (I don’t really know much about maps so sorry if this is a bad question). I’m interested in using a map for an inventory system that will contain item objects. An item object has a name, description, and money value. The key would be the item’s name, and the linking variable would be the the quantity of items I have for that particular item.

And if a map doesn’t work, does anyone have a good alternative to this type of system? I need something keeping track of the quantity of each type of item I have.

Answer 1

The C++ standard library template map is just a storage container so it can definitely be used with objects. The map will take your object as its templated argument parameter.

A map would work well for your inventory system. Use something like:

#include <pair>
#include <map>
#include <string>
#include <iostream>

class Item {
  public:
   Item(void) {}
   ~Item(void) {}
   Item(std::string new_name) {
      my_name=new_name;
   }
   void setName(std::string new_name) {
      my_name= new_name;
   }
   std::string getName(void) {
      return my_name;
   }
  private:
   std::string my_name;
};  

class Item_Manager {
  public:
   Item_Manager(void) {}
   ~Item_Manager(void) {}  
   void addItem(Item * my_item, int num_items) {
      my_item_counts.insert( std::pair<std::string,int>(Item.getName(),num_items) );
   }
   int getNumItems(std::string my_item_name) {
      return my_item_counters[my_item_name];
   }
  private: 
   std::map<std::string, int> my_item_counts;
};

main () {
   Item * test_item = new Item("chips");
   Item * test_item2 = new Item("gum");
   Item_Manager * my_manager = new Item_Manager();

   my_manager->addItem(test_item, 5);
   my_manager->addItem(test_item2,10);
   std::cout << "I have " << my_manager->getNumItems(test_item->getName())
             << " " << test_item->getName() << " and " 
             << my_manager->getNumItems(test_item2->getName())
             << " " << test_item2->getName() << std::endl;

   delete test_item;
   delete test_item2;
   delete my_manager;
}

Here’s a reference on the stdlib map and its functions:
http://www.cplusplus.com/reference/stl/map/

Look at the function pages for examples of how to iterate through/index a map, etc.