/// <summary>
/// Attempts to advance to a new state, checking for unknown and null states.
/// </summary>
/// <param name="nextState">The name of the state to go to (as sent to AddState).</param>
protected void AdvanceToState(String nextState)
{
// If they passed a value state name...
if (!String.IsNullOrEmpty(nextState))
{
// ...and it is one that we are managing.
if (mStates.ContainsKey(nextState))
{
// Request a new state and move to the END pass of this flow.
mNextState = mStates[nextState];
mCurrentFlowState = FlowStates.END;
}
else
{
System.Diagnostics.Debug.Assert(false, "FSMState returned a new state which is not managed by this state machine: " + nextState);
}
}
}
/// <summary>
/// Called by GameObjectFactory when object is recycled.
/// </summary>
public override void Reset()
{
mCurrentState = mNextState = mInitialState;
mCurrentFlowState = FlowStates.INITIAL_STATE;
}
/// <summary>
/// Interface for adding new FSMState to this FiniteStateMachine.
/// </summary>
/// <param name="state">Implementation of the FSMState.</param>
/// <param name="id">An indentifier used to manage and transition between states.</param>
protected void AddState(FSMState state, String id)
{
// The state will be expecting to access the Parent GameObject a lot.
state.pParentGOH = mParentGOH;
// Check for duplicate entries.
if (mStates.ContainsKey(id))
{
System.Diagnostics.Debug.Assert(false, "Attempting to add two FSMState objects with the same ID to a FiniteStateMachine: " + id);
return;
}
else
{
// Add it to our list of states.
mStates.Add(id, state);
}
// If this is the first state to be added, use it as the initial FSMState to be run.
if (mCurrentState == null)
{
mInitialState = mCurrentState = mNextState = state;
mCurrentFlowState = FlowStates.INITIAL_STATE;
}
}
/// <summary>
/// Called once per frame by the game object.
/// </summary>
/// <param name="gameTime">The amount of time that has passed this frame.</param>
public override void Update(GameTime gameTime)
{
// The basic flow for every state machine:
// 1) Run OnBegin (1 frame).
// 2) Run OnUpdate (Indefinitly; until it returns a new state to transition to).
// 3) Run OnEnd (1 frame).
//
switch (mCurrentFlowState)
{
case FlowStates.BEGIN:
{
// Transition directly to the UPDATE pass. Do it before calling OnBegin incase
// OnBegin actually sets the current state through a message, in which case we
// don't want to go to UPDATE.
mCurrentFlowState = FlowStates.UPDATE;
mCurrentState.OnBegin();
break;
}
case FlowStates.UPDATE:
{
// Update the state which will potentially return a new state in which to transition to.
String nextState = mCurrentState.OnUpdate();
AdvanceToState(nextState);
break;
}
case FlowStates.END:
{
mCurrentState.OnEnd();
// Once the FlowStates.END has finished it is time to move onto the next FSMState.
mCurrentState = mNextState;
// On the next update pass we will be running a new FSMState, so we want to be sitting
// in the BEGIN flow state.
mCurrentFlowState = FlowStates.BEGIN;
break;
}
default:
{
System.Diagnostics.Debug.Assert(false, "Unhandled FSM Flow State.");
break;
}
}
// Keep going until we get to an update state. This is to avoid objects popping out and
// in between states.
if (mCurrentFlowState != FlowStates.UPDATE)
{
Update(gameTime);
}
}