FSMTobo

Finite State Machine for Game Maker

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This is a little experiment that came to my mind while making a FSM in C#. I haven't done performance tests or anything like that, you can expect anything from this project. You can fork it and improve it or just let it disappear on the internet.

How to use it

Creating States

1. Each state is an object that is instantiated when the FSM is created. To create a state you have to create four scripts. (You can name it whatever you want.)

• Enter Script: It runs when the state is entered. This means that it runs once upon entering a state.
• Input Script: It runs all the time. Keyboard inputs could be handled here.
• Physics Script: It runs all the time. The physics or movements that respond to keyboard input is done here.
• Exit Script: It runs once just like the Enter Script when the state changes.

2. After that create an object (let's call it oState1) that will be your state and add the following code:

Create Event:

FSMStateInitialize(
   EnterScript,
   InputScript,
   PhysicsScript,
   ExitScript
   );

CleanUp State:

FSMStateCleanUp();

SetUp your FSM

1. Create an object that will be you FSM and add the following code:

Create Event:

//Initialize the FSM
FSMInitialize();

// All states of the FSM
var myState1 = instance_create_layer(0,0,"Instances",oState1);
var myState2 = instance_create_layer(0,0,"Instances",oState2);
// etc...

// Starting state
current = myState1;

Step Event:

FSMLoop(current,self);

Transitions

So far we have a FSM and a set of states. But there is still no relationship between states. Each state can have several edges and each one can have a different condition. To solve this, for every edge that has a state there must be a script that returns a boolean that indicates when it should change to another state. If it returns true, it changes to the state to which it is related.

For example, if we want to add a transition between two states myState1 and myState2, we could create a script called State1ToState2. In this script it would go all the conditions to go from state State1 to State2.

1. So, after the Create Event code we put the transitions (It would look something like this):

//Initialize the FSM
FSMInitialize();

// All states of the FSM
var myState1 = instance_create_layer(0,0,"Instances",oState);
var myState2 = instance_create_layer(0,0,"Instances",oState2);
// etc...

// Starting state
current = myState;

// Transitions (state, conditions, state to go)
FSMAddTransition(myState1,State1ToState2,myState2)

PS: Sorry for my English, but it is not my mother tongue. :P