Using File IO to Save and Load Games - Learn C++ for Game Development - page 241

if (iter != m_serializables.end())
{
iter->second->OnLoad(file);
}
}
}
}
else
{
found = false;
}
}
return found;
}
The Load method is a little more involved than Save . You can see that it is using an ifstream , input
file stream , rather than an ofstream . The ifstream is initialized using the file name to load. The
is_open method in ifstream is used to determine if a file with the given name was found. If the
player has never played the game, then no save file will exist; this check ensures that we do not try
to load a game when no save game exists.
The next check is used to determine if the save file that does exist has a valid save state inside. This
is done using the >> operator, just as is done when using cin . This is what happens next when cin is
used to ask the player if he or she would like to load the save game. If the player types anything but
yes, then game will start without loading.
There is then a while loop that is checking if the eof method is returning true . The eof method is
determining whether the method has hit the end of file . The inner section of this loop reads the
unique ID from the file, retrieves the Serializable from the map, and then calls the OnLoad method
on that object.
The last SerializationManager method is ClearSave , which is used to write out a file with false as
its only value. Listing 24-5 shows this method.
Listing 24-5. The SerializationManager::ClearSave Method
void SerializationManager::ClearSave()
{
std::ofstream file{ m_filename };
file << false;
}
The SerializationManager class is fairly simple. The Serializable class is also straightforward
and is listed in Listing 24-6.
Listing 24-6. The Serializable Class
class Serializable
{
unsigned int m_id{ 0 };