FSM

Introduction

Finite state machine.

• Author: Rex
• Object

Usage

Sample code

Install plugin

Load minify file

• Load plugin (minify file) in preload stage

  scene.load.plugin('rexfsmplugin', 'https://raw.githubusercontent.com/rexrainbow/phaser3-rex-notes/master/dist/rexfsmplugin.min.js', true);
  

• Add FSM object

  var state = scene.plugins.get('rexfsmplugin').add(config);
  

Import plugin

• Install rex plugins from npm

  npm i phaser3-rex-plugins
  

• Install plugin in configuration of game

  import FSMPlugin from 'phaser3-rex-plugins/plugins/fsm-plugin.js';
  var config = {
      // ...
      plugins: {
          global: [{
              key: 'rexFSM',
              plugin: FSMPlugin,
              start: true
          },
          // ...
          ]
      }
      // ...
  };
  var game = new Phaser.Game(config);
  

• Add FSM object

  var state = scene.plugins.get('rexFSM').add(config);
  

Import class

• Install rex plugins from npm

  npm i phaser3-rex-plugins
  

• Import class

  import FSM from 'phaser3-rex-plugins/plugins/fsm.js';
  

• Add FSM object

  var state = new FSM(config);
  

Create instance

Create by config

var state = scene.plugins.get('rexFSM').add({
    start: 'A',   // default: undefined
    states: {
        A: {
            next: 'B',  // function() { return 'B'; }
            enter: function() {},
            exit: function() {}
        },
        // ...
    },
    init: function() {},
    extend: {
        i: 0,
        name: 'abc'
        // ...
    },
    enable: true,
    eventEmitter: undefined
});

• start: Initial state.
• states: Define states.
  • stateName
    • next: String of next state, or a callback to get next state.
    • enter: Callback when enter state.
    • exit: Callback when exit state.
• init: Initial callback when creating instance.
• extend: Inject key-value pairs into instance.
• enable: Set false to block any state changing.
• eventEmitter
  • undefined : Create a private event emitter, default value.
  • false : Don't add any event emitter, i.e. no event will be fired.
  • Event emitter object : Fire event through this event emitter.

Inheritance

1. Create new class

   class State extends FSM {
       constructor() {
           super();
       }
   
       next_A() { return 'B' }
   
       enter_A() { /* ... */ }
   
       exit_A() { /* ... */ }
   }
   

   Members: - next_ + stateName: Callback to get next state. - enter_ + stateName: Callback when enter state. - exit_ + stateName: Callback when exit state.
2. Create instance

   var state = new State();
   

Read state

• Current state

  var curState = state.state;
  

• Previous state

  var preState = state.prevState;
  

Start at state

Set new state without triggering any state-changing callbacks or events.

state.start(newState);

Next state

graph TB

next["state.next()"] --> next_A["state.next_A()<br>return 'B'"]

next_A --> eventStateChange["state.emit('statechange', state)<br>state.prevState -> state.state"]

subgraph State changing

eventStateChange --> exit_A["state.exit_A()"]
exit_A --> eventExitA["state.emit('exit_A', state)"]

eventExitA --> enter_B["state.enter_B()"]
enter_B --> eventEnterB["state.emit('enter_B', state)"]

subgraph Exit
exit_A
eventExitA
end

subgraph Enter
enter_B
eventEnterB
end

end

goto["state.goto('B')"] --> eventStateChange

subgraph Request

subgraph Next
next
next_A
end

subgraph Goto
goto
end

end

Request

• Get next state by callback

  state.next();    // nextState = state.next_A()    
  

• Goto state

  state.goto(nextState);
  // state.state = nextState;
  

State-changing

These callbacks or events will be triggered if state is changing.

For example, state is changing from 'A' to 'B'.

1. event statechange

   state.on('statechange', function(state) {
       console.log( state.prevState + '->' + state.state );
   });
   

2. callback state.exit_A
3. event exit_A

   state.on('exit_A', function(state) {
       /*...*/
   });
   

4. callback state.enter_B
5. event enter_B

   state.on('enter_B', function(state) {
       /*...*/
   });
   

Enable

state.setEnable();
// state.setEnable(false); // disable

or

state.toggleEnable();

state.next() and state.goto() will be ignored if disabled.

Add new state

state.addState(name, {
    next: 'B',  // function() { return 'B'; }
    enter: function() {},
    exit: function() {}
})

or

state.addStates({
    'D' : {
        next: 'B',  // function() { return 'B'; }
        enter: function() {},
        exit: function() {}
    },
    // ...
})