The Stateful ElePHPant

State machines and the state pattern seem to be pretty underestimated in the PHP world. Most examples found are of doors and other objects that have no application in most of our projects. Starting the talk I will be explaining what the state pattern is and how it's used in a game. Then we'll be discovering what this can do for us in the world of web applications. Following that we're taking a brief look at the state machine, how it's different from the pattern and why it's useful to us.

Instead of simply presenting you these concepts I prefer doing a live coding session so we can explore the possibilities together. You will be walking away from this talk with a solid understanding of the state pattern/state machine and the knowledge on when you should apply these concepts. There will also be plenty of time to have your questions answered.

At the end of the presentation I will also provide a list of useful resources that can help you introduce these concepts within your own projects.

Transcript

1. THE STATEFUL ELEPHPANT RICK KUIPERS / @RSKUIPERS @PHPSTORMTIPS
2. THE STATEFUL ELE ANT PHP C# RUBY PYTHON SCALA JAVA JAVASCRIPT GO PASCAL
3. ++++++++++[>+++++++>++++++++++>+++>+<<<<-]>+ +.>+.+++++++..+++.>++.<<+++++++++++++++.>.++ +.------.--------.>+.>. HAI 1.2 CAN HAS STDIO? VISIBLE "HAI WORLD!" KTHXBYE
4. TOPICS ! STATE ! STATE DIAGRAM ! STATE MACHINES ! STATE PATTERN
5. STATE
6. THE GAME
7. STATE DIAGRAM
8. ini#al state 10101 accep#ng state ✅ 01110 DETERMINISTIC FINITE AUTOMATON state transi#on ACCEPTOR
9. DETERMINISTIC FINITE AUTOMATON TRANSDUCER MEALY
10. DETERMINISTIC FINITE AUTOMATON TRANSDUCER MEALY
11. FINITE STATE ACCEPTOR
12. STATUSES PENDING NEW COMPLETED CANCELED REFUNDED
13. DETERMINISTIC FINITE AUTOMATON ACCEPTOR
14. $order = $this->getOrder(); $order->setStatus(Order::STATUS_COMPLETED);
15. [ 'transitions' => [ 'create' => [ 'from' => ['new'], 'to' => 'pending', ], 'cancel' => [ 'from' => ['new', 'pending'], 'to' => 'canceled', ], 'complete' => [ 'from' => ['pending'], 'to' => 'completed', ], 'refund' => [ 'from' => ['completed'], 'to' => 'refunded', ], ], ];
16. $order = $this->getOrder(); $stateMachine = $stateMachineFactory->get($order); $stateMachine->apply('complete');
17. $order = $this->getOrder(); $stateMachine = $stateMachineFactory->get($order); $stateMachine->apply('complete'); $stateMachine->apply('cancel'); PHP FATAL ERROR: UNCAUGHT SM\SMEXCEPTION: TRANSITION "CANCEL" CANNOT BE APPLIED ON STATE "COMPLETED" OF OBJECT "ORDER" WITH GRAPH "DEFAULT"
18. Complete Refund Cancel $sm->can('cancel'); true $sm->can('refund'); false $sm->can('complete'); true
19. Complete Refund Cancel $sm->can('cancel'); false $sm->can('refund'); true $sm->can('complete'); false
20. Complete Refund Cancel $sm->can('cancel'); false $sm->can('refund'); false $sm->can('complete'); false
21. [ 'callbacks' => [ 'after' => [ 'refund' => [ ['Inventory\Callback\Refund', 'onRefund'], ], ], ], ];
22. THE STATE PATTERN
23. if (cursors.left.isDown) { player.body.velocity.x = -150; player.scale.x = 1; player.animations.play('left'); if (player.body.touching.down) { state.text = 'running'; } } else if (cursors.right.isDown) { player.body.velocity.x = 150; player.scale.x = -1; player.animations.play('right'); if (player.body.touching.down) { state.text = 'running'; } } else { player.animations.stop(); player.frame = 2; if (player.body.touching.down) { state.text = 'idling'; } } if (game.input.keyboard.isDown(Phaser.Keyboard.SPACEBAR) && player.body.touching.down) { player.body.velocity.y = -350; state.text = 'jumping'; }
24. THE GAME WITH STATE PATTERN
25. var Elephpant = function(player) { this.state = new Idling(this, player); this.shoot = function() { // Shoot gigantic fireball }; this.transitionTo = function(state) { this.state = state; }; this.handle = function(input) { this.state.process(input); this.state.display(input); }; };
26. var Idling = function(elephpant, player) { this.display = function() { player.body.velocity.x = 0; player.animations.stop(); player.frame = 2; }; this.process = function(input) { if (input.left.isDown || input.right.isDown) { elephpant.transitionTo(new Running(elephpant, player)); return; } if (input.up.isDown) { elephpant.transitionTo(new Jumping(elephpant, player)); return; } if (input.space.isDown) { elephpant.shoot(); } }; };
27. var Jumping = function(elephpant, player) { this.display = function() { if (player.body.touching.down) { player.body.velocity.y = -350; } }; this.process = function(input) { if (!input.up.isDown && player.body.touching.down) { elephpant.transitionTo(new Idling(elephpant, player)); } }; };
29. THE STATE STRATEGY PATTERN?
30. STRATEGY PATTERN ! Tries to achieve similar result for input ! Strategies can’t transition to other
 strategies ! Strategy processes the input and gives
 output to the caller STATE PATTERN ! Result can be completely different ! States can trigger transitions to other
 states ! State controls the behaviour of its
 wrapper
31. WHY SHOULD WE CARE?
32. CHECKOUT PAYMENT DETAILS REVIEW
33. EXAMPLE
36. RECAP FINITE STATE ACCEPTOR STATE PATTERN ! Monolith ! Acceptor (pa9ern matching) ! Is this a valid transi#on? ! Transi#ons are set in stone ! Callbacks are easy to implement ! Object Oriented ! Transducer (controlling) ! Different behaviour per state ! Reduces the amount of condi#onals
37. PACKAGES DON’T REINVENT THE WHEEL ! https://github.com/winzou/state-machine ! https://github.com/Sylius/SyliusFlowBundle ! https://github.com/rskuipers/stateful-elephpant ! https://github.com/rskuipers/stateful-elephpant-talk ! https://github.com/rskuipers/stateful-elephpant-expressive
38. 4 @RSKUIPERS RICK KUIPERS QUESTIONS? RSKUIPERS@ENRISE.COM HTTPS://JOIND.IN/TALK/26C09