UGTK / Toolkit / Design Patterns / State Machine Completed

State Machine

Summary

The State Machine is a system for managing and transitioning between different states in a game. It allows for the definition of states and the conditions under which transitions occur, providing advanced control over state changes and associated events.

Modules Dependencies

The State Machine module requires the following dependencies:

EventSystem: Manages events for state transitions.

Ensure that these dependencies are correctly imported and configured in your project.

Carried inside the prefabs. These modules are not referenced by the assembly definition - the components are simply already attached to the prefabs this module ships. Remove one of them from the project and the prefab keeps its layout and loses that behaviour, with nothing in the console to say so.

Module	Component, and the prefab carrying it
`UtilitySystems/PoolingSystem`	`Mn_Pooler` (in `StateMachineController`)

Setup

To set up the State Machine, follow these steps:

Add State Machine Controller prefab to your scene:

States

Add State prefab as child of State Machine:

Add Functs to the state

Decide the condition for entering in an other state

StateMachine

Set Starting State

Add Functs to State Changed:

How To Use

To use the State Machine, you will need code for changing state. You can use the call of an event, or by forcing the change state

Initialize State Machine adding the reference of the controller the state machine change the states:


    var obj;
    stateMachine.Initialize(obj);

Change State by Event:


    stateMachine.InvokeStateEvent("MyEventName");

Change State by forcing the trigger:


    Mn_State myState;
    stateMachine.ChangeState(myState);

Get CurrentState


    Mn_State myState = stateMachine.GetCurrentState();

Get Obj


    var myObj = stateMachine.GetObj();

Testing Scene

Open StateMachineScene in the module's folder and select StateMachineController > StateMachine. The Editor Test Tools block needs Play mode: the current state is a runtime thing, and outside Play the block says so instead of showing a stale name.

What to do, in order:

Play and watch the machine move between states.
Force a transition from the inspector into a state you have not reached yet.
Send an event name that no condition listens for.
Force the machine into the state it is already in.

Step 2 is what makes a late state testable without replaying everything that leads to it. Step 3 shows the silent case: an event with no matching condition does nothing at all, which is how a typo in an event name hides. Step 4 decides whether re-entering a state runs its enter callback again — worth knowing before an animation restarts unexpectedly.