Using the STL in Text Adventure - Learn C++ for Game Development - page 179

The Evaluate method is where the Chest::Open call is made. The method first checks to see if the
Chest is closed; if it is, then the Open call is made and the Item pointer is passed to Player::AddItem .
The last task is to print a message informing the player which Item was obtained from the Chest .
The Evaluate method brings us nicely to our next example of STL containers in our game. The Player
class requires storage for the Item objects that the user can obtain. You can see in Listing 19-11
that a vector<Item*> has been added to the Player class.
Listing 19-11. The Player Class's Item vector
class Player
: public Entity
{
private:
using Items = std::vector<Item*>;
Items m_items;
void AddItem(const Item* item)
{
m_items.push_back(const_cast<Item*>(item));
}
bool HasWeapon()
{
bool hasWeapon = false;
for (const Item* item : m_items)
{
const Sword* sword = dynamic_cast<const Sword*>(item);
if (sword != nullptr)
{
hasWeapon = true;
break;
}
}
return hasWeapon;
}
};
Listing 19-11 only shows the new code that has been added to Player . We now have an alias for the
Item* vector , the vector instance and two new methods, AddItem and HasWeapon .
AddItem is simply used to push new items onto the m_items vector. The HasWeapon method is a little
more interesting. It uses a dynamic_cast to determine if the current Item pointer is actually a Sword
class. A dynamic_cast will return nullptr if the type conversion is invalid; therefore, only objects that
are actually Swords will successfully return a valid Sword pointer. Once we have a valid Sword pointer
we know that the player has a weapon, so hasWeapon can be set to true and we can break out of our
loop. The loop in question is a range-based for loop that takes advantage of our STL class.
The Player class has a method to determine whether the player is armed or not because we are
going to add enemies to some of the Room objects. Listing 19-12 shows the Enemy class.