Game State Management - Learning C# by Programming Games - page 280

Inside the constructor, we initially assign null to the current game state, since no
game state can be selected yet. We then add a few methods and properties to add
and retrieve game states based on their string identifier. Since these methods are
quite straightforward, we will not discuss the details here, but you can have a look
at the code by opening the PenguinPairs3 program in the solution belonging to this
chapter.
The main method used for switching between game states is the SwitchTo method.
This method takes a string as a parameter and switches to the corresponding game
state. This is the complete method:
public void SwitchTo( string name)
{
if (gameStates.ContainsKey(name))
currentGameState = gameStates[name];
}
Inside this method, we check if the provided key exists. If it does, we set the current
game state to the state associated with that key.
As you can see, it is relatively easy to check if a dictionary contains a key or not.
What if we wanted to check if a dictionary contains a certain value ? In that case, we
have to do a search ourselves using the foreach -instruction. The kind of object that
foreach provides while traversing a dictionary is a KeyValuePair<> . This type contains
the properties Key and Value to access the key and value in the pair. Once we find the
current game state, we are done. Suppose that we are looking for the name of the
state currentGameState . This piece of code returns the key associated with that game
state:
foreach (KeyValuePair< string , IGameLoopObject> pair in gameStates)
{
if (pair.Value == currentGameState)
return pair.Key;
}
return "";
Going back to our game example, we still have to handle the different game loop
methods. This is actually relatively simple. If a game state is currently selected, we
simply call the game loop methods on the game state. For example, the HandleInput
method is given as follows:
public void HandleInput(InputHelper inputHelper)
{
if (currentGameState != null )
currentGameState.HandleInput(inputHelper);
}
We follow a similar procedure for the other game loop methods.