I think you may be getting a little bogged down in the English meaning of state, when compared to the State Pattern (or Finite-State Machine, which is really a diagrammatic representation of a State Pattern). Both are appropriate here, but they shouldn't be confused.
The State Pattern is something which should, given various common stimuli, operate on the game state differently at different times in the game. So, as you've rightly concluded, the lobby stage (which I'm assuming to be while people are joining a game) is a State in that context.
The game state is a list of players, pieces, cards, dice, whatever else, and all the information required to simulate them. You might want to call that the context.
Each State should receive a UserClicked message from the application which receives the context and coordinates or area clicked and should operate on those accordingly. The information that you are trying to give ownership of to the State object does not belong there, it belongs in the game itself, alongside the State.
The state may also have a UserPressedKey method, a TimerTicked method or any other kind of stimulus on which it should act. But each of these should act on the game state rather than being the game state.
One important method of the State will be ScreenRefresh, which will draw the context for the user.
Here is a very rough example:
abstract class ApplicationState {
void Begin(GameContext context);
void UserClicked(GameContext context, int x, int y);
void UserPressedKey(GameContext context, char key);
void TimerTicked(GameContext context);
void ScreenRefresh(GameContext context);
protected void OnStateChanged(ApplicationState newState) {
// inform interested parties that state has changed,
// using the observer pattern
}
}
class LobbyState : ApplicationState
{
void Begin(GameContext context) {
context.Players = new User[context.NoOfPlayers];
}
void UserClicked(GameContext context, int x, int y) {
// Find a displayed player box which contains click coords
int index = -1;
for (i=0; i < context.Players.Length; i++) {
if (PlayerBox[i].Contains(x, y)) {
index = i;
}
}
if (index > -1) {
if (context.Player[index] == null) {
context.Player[index] = context.ActivePlayer;
} else if (context.Player[index] == context.ActivePlayer()) {
context.Player[index] = null;
} else {
ErrorSound.Play();
}
} else if (CloseIcon.Contains(x, y)) {
OnStateChanged(new ExittingState());
} else {
ErrorSound.Play();
}
}
void UserPressedKey(GameContext context, char key) {
if (key = 'J' or key = 'j') {
if (! context.AddPlayerRandomly(context.ActiveUser)) {
ErrorSound.Play();
}
if (context.GameIsNowFull()) {
OnStateChanged(new InitializingState());
}
} else if key = Esc {
if (!context.RemovePlayer(context.ActiveUser)) {
ErrorSound.Play();
}
} else {
ErrorSound.Play();
}
}
void TimerTicked(GameContext context) {
// there is no use for a game timer while
// we're trying to fill the game, but you
// want one to tick anyway, because the
// application doesn't know which state
// it is in.
}
void ScreenRefresh(GameContext context) {
DrawPlayerBoxes(context.Screen, context.Players);
DrawExitIcon(context.Screen);
}
}
class InitializingState : ApplicationState {
private double waitSpinnerAngle = 0;
void Begin(GameContext context) {
context.RandomizePlayOrder();
context.ShuffleCards();
// all other game initialization rules here
OnContextChanged(new PlayerUpState(context.Players[0]));
}
void UserClicked(GameContext context, int x, int y) {
// Not responding to user input for a moment
ErrorSound.Play();
}
void UserPressedKey(GameContext context, char key) {
// Not responding to user input for a moment
ErrorSound.Play();
}
void TimerTicked(GameContext context) {
waitSpinnerAngle += 0.05;
if (waitSpinnerAngle > 1) waitSpinnerAngle = 0;
}
void ScreenRefresh(GameContext context) {
DrawWaitSpinner(waitSpinnerAngle);
}
}
See where I'm going with this? The Application itself is then as simple as setting the initial State, hooking a listener into the OnStateChanged event and calling Begin. When the listener hears that the event is called, unhook your old State, hook in the new one, and call Begin again.
Everything else is triggered by events from the mouse, keyboard or timer, passed directly to the current State without knowledge of which State the game is currently in. If you are running this game across a network then you will also need an event for changes of state received from other players.
Everything in your State and Context is now very unit-testable and separation of concerns are observed. Although, you may want to refactor that LobbyState#UserClicked method a bit, among other things.
Remember, this is just a free example and you get what you paid for it. Don't try to apply it directly to your game. Just use it to understand how the State Pattern should work in the context of a game.
First of all, I'd always avoid global state unless it is absolutely necessary. It makes extended your code hard, testing your code hard, and debugging your code hard. For the expense of having a state machine object that is passed to each state when it's created? Definitely not.
But I don't think it's necessary anyway. Your code has another antipattern that you haven't highlighted: your State objects cause side-effects in their constructors, which is a seriously bad idea. I'd fix both problems with a single change: have a class StateMachine with a method:
void changeState(State * requested)
{
State * alternative;
while (alternative = requested-> getAlternative ())
requested = alternative;
currentState = requested;
}
Where getAlternative is a virtual method in State that returns null, and can be overridden by each subclass to return a different state if necessary.
Once this is done, you can allocate a single instance of each State subclass and use those rather than calling "new" all the time, which will save the possibility of memory leaks (which look like they could have been a problem in your design).
Best Answer
The Wikipedia article for State Pattern has a Java example that illustrates two states, involving two different methods. Those methods can be arbitrarily complex, so I consider a two-state solution (no pun intended) perfectly valid.
Note that
writeNameswaps out its own implementation by handing a newStateLikeobject to theStateContextwhen theicount exceeds one.A State Pattern would be indicated if your "machinery" substantially changes between states. The complexity of the condition needed to choose the correct processing object doesn't matter; it's the complexity of the state objects themselves that are the deciding factor. Otherwise, you could just write all of the logic into a single class.
Think about what happens when you build a car. The chassis moves along an assembly line and stops at a station where the welding takes place. Once that state has completed, the chassis moves to the next station on the assembly line, where a different set of robots with completely different programming installs the engine.