Fear Not the Machine of State!

Do your application’s objects have properties like ‘status’ or ‘state’, boolean properties like ‘active’, ‘paid’ or ‘published’, nullable timestamp properties like ‘paid_on’ or ‘published_at’? These are all good indicators that your project may benefit from the introduction of a State Machine. Proper use of a State Machine can mean less bugs, less undefined behavior, and a more clearly defined API to your object’s internal state, yet many developers are reluctant to use them in their projects, fearing unnecessary complexity, difficult integration or a steep learning curve. The good news is that these concerns are largely unfounded! Join us as we explore the State Machine’s theoretical underpinnings, examine its practical application including examples of its use in popular open source projects, and review available PHP resources for easily leveraging the power of the State Machine in your own projects.

1. Fear Not the Machine of State!
3. Yitzchok Willroth
4. Yitzchok Willroth
5. Yitzchok Willroth @coderabbi
6. Yitzchok Willroth @coderabbi
7. Yitzchok Willroth @coderabbi
19. State Pattern
20. State Pattern • Behavioral Pattern
21. State Pattern • Behavioral Pattern • Allows an object to alter its behavior when its internal state changes, giving the appearance of changing class.
31. Context: maintains an instance of the concrete state subclass that defines current behavior. Abstract State: defines an interface for encapsulating all state behavior. Concrete State: implements the behavior associated with a state of the context.
35. IDENTIFY STATES
37. Locked Coin Unlock Pass Lock Unlocked
38. Locked Coin Unlock Pass Lock Unlocked
40. IDENTIFY TRANSITIONS
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43. Locked Coin Unlock Pass Lock Unlocked
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46. Locked Coin Unlock Pass Lock Unlocked
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49. Locked Coin Unlock Pass Lock Unlocked
52. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
53. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
54. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
55. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
56. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
57. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
58. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
59. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
60. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
61. class Turnstyle { const LOCKED_STATE = 'locked'; const UNLOCKED_STATE = 'unlocked'; private $status; public function __construct($status = null) { $this->status = is_null($status) ? self::LOCKED_STATE : $status; } public function getStatus() { return $this->status; } public function pass() { $this->status = self::LOCKED_STATE; } public function coin() { $this->status = self::UNLOCKED_STATE; } }
64. Locked Coin Unlock Pass Lock Unlocked
65. Locked Coin Unlock Pass Lock Unlocked Pass
66. Locked Coin Unlock Pass Lock Unlocked Pass Alarm
67. Locked Coin Unlock Pass Lock Unlocked Pass Alarm
68. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin
69. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund
70. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund
73. // truncated ... public function pass() { if ($this->status == self::LOCKED_STATE) { $this->alarm->sound(); } $this->status = self::LOCKED_STATE; } public function coin() { if ($this->status == self::UNLOCKED_STATE) { $this->coinVendor->refund(); } $this->status = self::UNLOCKED_STATE; } // truncated ...
74. // truncated ... public function pass() { if ($this->status == self::LOCKED_STATE) { $this->alarm->sound(); } $this->status = self::LOCKED_STATE; } public function coin() { if ($this->status == self::UNLOCKED_STATE) { $this->coinVendor->refund(); } $this->status = self::UNLOCKED_STATE; } // truncated ...
75. // truncated ... public function pass() { if ($this->status == self::LOCKED_STATE) { $this->alarm->sound(); } $this->status = self::LOCKED_STATE; } public function coin() { if ($this->status == self::UNLOCKED_STATE) { $this->coinVendor->refund(); } $this->status = self::UNLOCKED_STATE; } // truncated ...
76. // truncated ... public function pass() { if ($this->status == self::LOCKED_STATE) { $this->alarm->sound(); } $this->status = self::LOCKED_STATE; } public function coin() { if ($this->status == self::UNLOCKED_STATE) { $this->coinVendor->refund(); } $this->status = self::UNLOCKED_STATE; } // truncated ...
77. // truncated ... public function pass() { if ($this->status == self::LOCKED_STATE) { $this->alarm->sound(); } $this->status = self::LOCKED_STATE; } public function coin() { if ($this->status == self::UNLOCKED_STATE) { $this->coinVendor->refund(); } $this->status = self::UNLOCKED_STATE; } // truncated ...
80. Locked Coin Unlock Pass Lock Unlocked Coin Refund
81. Locked Coin Unlock Pass Lock Unlocked Coin Refund Violation
82. Locked Coin Unlock Pass Lock Unlocked Pass Coin Refund Violation
83. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation
84. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation
85. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Ready
86. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Ready ResetAlarm
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88. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Ready ResetAlarm Lock
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100. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Reset ResetAlarm Ready ResetAlarm Lock NORMAL MODE Coin Refund Pass
101. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Reset ResetAlarm Ready ResetAlarm Lock NORMAL MODE Coin Refund Pass
102. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Reset ResetAlarm Ready ResetAlarm Lock NORMAL MODE DIAGNOSTIC MODE Coin Refund Pass
103. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Reset ResetAlarm Ready ResetAlarm Lock NORMAL MODE DIAGNOSTIC MODE H Coin Refund Pass
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106. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund
109. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
110. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
111. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
112. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
113. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
114. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
115. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
116. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
117. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
118. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
119. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
120. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
121. class Turnstile { private $state; public $lockedState; public $unlockedState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } }
123. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } }
124. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } }
125. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } }
126. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } }
127. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } }
129. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
130. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
131. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
132. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
133. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
134. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
135. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
136. class LockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
138. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
139. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
140. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
141. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
142. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
143. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
144. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
145. class unlockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->setState($turnstile->lockedState); } public function coin(Turnstile $turnstile) { $turnstile->coinVendor->refund(); } }
148. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund
149. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Reset ResetAlarm Ready ResetAlarm Lock Coin Refund Pass
152. class Turnstile { private $state; public $lockedState; public $unlockedState; public $violationState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->violationState = new ViolationTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } public function reset() { $this->state->reset($this); } public function ready() { $this->state->ready($this); } }
153. class Turnstile { private $state; public $lockedState; public $unlockedState; public $violationState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->violationState = new ViolationTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } public function reset() { $this->state->reset($this); } public function ready() { $this->state->ready($this); } }
154. class Turnstile { private $state; public $lockedState; public $unlockedState; public $violationState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->violationState = new ViolationTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } public function reset() { $this->state->reset($this); } public function ready() { $this->state->ready($this); } }
155. class Turnstile { private $state; public $lockedState; public $unlockedState; public $violationState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->violationState = new ViolationTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } public function reset() { $this->state->reset($this); } public function ready() { $this->state->ready($this); } }
156. class Turnstile { private $state; public $lockedState; public $unlockedState; public $violationState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->violationState = new ViolationTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } public function reset() { $this->state->reset($this); } public function ready() { $this->state->ready($this); } }
157. class Turnstile { private $state; public $lockedState; public $unlockedState; public $violationState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->violationState = new ViolationTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } public function reset() { $this->state->reset($this); } public function ready() { $this->state->ready($this); } }
158. class Turnstile { private $state; public $lockedState; public $unlockedState; public $violationState; public function __construct(TurnstileState $state = null) { $this->lockedState = new LockedTurnstileState(); $this->unlockedState = new UnlockedTurnstileState(); $this->violationState = new ViolationTurnstileState(); $this->state = is_null($state) ? $this->lockedState : $state; } public function getState() { return $this->state; } public function setState(TurnstileState $state) { $this->state = $state; } public function pass() { $this->state->pass($this); } public function coin() { $this->state->coin($this); } public function reset() { $this->state->reset($this); } public function ready() { $this->state->ready($this); } }
160. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } public function reset(Turnstile $turnstile) { //empty implementation } public function ready(Turnstile $turnstile) { //empty implementation } }
161. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } public function reset(Turnstile $turnstile) { //empty implementation } public function ready(Turnstile $turnstile) { //empty implementation } }
162. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } public function reset(Turnstile $turnstile) { //empty implementation } public function ready(Turnstile $turnstile) { //empty implementation } }
163. abstract class TurnstileState { public function pass(Turnstile $turnstile) { //empty implementation } public function coin(Turnstile $turnstile) { //empty implementation } public function reset(Turnstile $turnstile) { //empty implementation } public function ready(Turnstile $turnstile) { //empty implementation } }
165. class violationTurnstileState implements TurnstileState { public function coin(Turnstile $turnstile) { turnstile->coinVendor->refund(); } public function reset(Turnstile $turnstile) { $turnstile->alarm->reset(); } public function ready(Turnstile $turnstile) { $turnstile->alarm->reset(); $turnstile->setState($turnstile->unlockedTurnstileState); } }
166. class violationTurnstileState implements TurnstileState { public function coin(Turnstile $turnstile) { turnstile->coinVendor->refund(); } public function reset(Turnstile $turnstile) { $turnstile->alarm->reset(); } public function ready(Turnstile $turnstile) { $turnstile->alarm->reset(); $turnstile->setState($turnstile->unlockedTurnstileState); } }
167. class violationTurnstileState implements TurnstileState { public function coin(Turnstile $turnstile) { turnstile->coinVendor->refund(); } public function reset(Turnstile $turnstile) { $turnstile->alarm->reset(); } public function ready(Turnstile $turnstile) { $turnstile->alarm->reset(); $turnstile->setState($turnstile->unlockedTurnstileState); } }
168. class violationTurnstileState implements TurnstileState { public function coin(Turnstile $turnstile) { turnstile->coinVendor->refund(); } public function reset(Turnstile $turnstile) { $turnstile->alarm->reset(); } public function ready(Turnstile $turnstile) { $turnstile->alarm->reset(); $turnstile->setState($turnstile->unlockedTurnstileState); } }
169. class violationTurnstileState implements TurnstileState { public function coin(Turnstile $turnstile) { turnstile->coinVendor->refund(); } public function reset(Turnstile $turnstile) { $turnstile->alarm->reset(); } public function ready(Turnstile $turnstile) { $turnstile->alarm->reset(); $turnstile->setState($turnstile->unlockedTurnstileState); } }
170. class violationTurnstileState implements TurnstileState { public function coin(Turnstile $turnstile) { turnstile->coinVendor->refund(); } public function reset(Turnstile $turnstile) { $turnstile->alarm->reset(); } public function ready(Turnstile $turnstile) { $turnstile->alarm->reset(); $turnstile->setState($turnstile->unlockedTurnstileState); } }
172. class lockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); $turnstile->setState($turnstile->violationState); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
173. class lockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); $turnstile->setState($turnstile->violationState); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
174. class lockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); $turnstile->setState($turnstile->violationState); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
175. class lockedTurnstileState extends TurnstileState { public function pass(Turnstile $turnstile) { $turnstile->alarm->sound(); $turnstile->setState($turnstile->violationState); } public function coin(Turnstile $turnstile) { $turnstile->setState($turnstile->unlockedState); } }
178. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Reset ResetAlarm Ready ResetAlarm Lock Coin Refund Pass
179. Locked Coin Unlock Pass Lock Unlocked Pass Alarm Coin Refund Violation Reset ResetAlarm Ready ResetAlarm Lock NORMAL MODE DIAGNOSTIC MODE H Coin Refund Pass
181. Extend the public API of the “context” & Abstract “state” classes To include new event triggers
182. Extend the public API of the “context” & Abstract “state” classes To include new event triggers Create a concrete subclass of the abstract “state class” to encapsulate the new state logic
183. Extend the public API of the “context” & Abstract “state” classes To include new event triggers Create a concrete subclass of the abstract “state class” to encapsulate the new state logic ADD an instance of the new concrete “state” class as an instance variable on the “context” object
185. Flexibility
186. CONTROL
187. VISIBILITY
194. • State Variables
195. • State Variables • $status
196. • State Variables • $status • $state
197. • State Variables • $status • $state • Boolean Driven Development
198. • State Variables • $status • $state • Boolean Driven Development • $active, $published
199. • State Variables • $status • $state • Boolean Driven Development • $active, $published • isActive(), isPublished()
200. • State Variables • $status • $state • Boolean Driven Development • $active, $published • isActive(), isPublished() • Nullable Timestamps
201. • State Variables • $status • $state • Boolean Driven Development • $active, $published • isActive(), isPublished() • Nullable Timestamps • Multipart Conditionals or Switches
217. github.com/sebastianbergmann/state
220. <?xml version="1.0" encoding="UTF-8"?> <specification> <configuration> <class name="Door"/> <interface name="DoorState"/> <abstractClass name="AbstractDoorState"/> </configuration> <states> <state name="OpenDoorState" query="isOpen"/> <state name="ClosedDoorState" query="isClosed"/> <state name="LockedDoorState" query="isLocked"/> </states> <transitions> <transition from="ClosedDoorState" to="OpenDoorState" operation="open"/> <transition from="OpenDoorState" to="ClosedDoorState" operation="close"/> <transition from="ClosedDoorState" to="LockedDoorState" operation="lock"/> <transition from="LockedDoorState" to="ClosedDoorState" operation="unlock"/> </transitions> <operations> <operation name="open" allowed="canBeOpened" disallowed="cannotBeOpened"/> <operation name="close" allowed="canBeClosed" disallowed="cannotBeClosed"/> <operation name="lock" allowed="canBeLocked" disallowed="cannotBeLocked"/> <operation name="unlock" allowed="canBeUnlocked" disallowed="cannotBeUnlocked"/> </operations> </specification>
222. OpenDoor [x] Can be closed [x] Cannot be opened [x] Cannot be locked [x] Cannot be unlocked ClosedDoor [x] Cannot be closed [x] Can be opened [x] Can be locked [x] Cannot be unlocked LockedDoor [x] Cannot be closed [x] Cannot be opened [x] Cannot be locked [x] Can be unlocked
224. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
225. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
226. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
227. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
228. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
229. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
230. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
231. class Door { private $state; public function __construct(DoorState $state) { $this->setState($state); } public function open() { $this->setState($this->state->open()); } public function close() { $this->setState($this->state->close()); } public function lock() { $this->setState($this->state->lock()); } public function unlock() { $this->setState($this->state->unlock()); } private function setState(DoorState $state) { $this->state = $state; } }
233. class ClosedDoorState extends AbstractDoorState { public function open() { return new OpenDoorState; } public function lock() { return new LockedDoorState; } }
234. class ClosedDoorState extends AbstractDoorState { public function open() { return new OpenDoorState; } public function lock() { return new LockedDoorState; } }
235. class ClosedDoorState extends AbstractDoorState { public function open() { return new OpenDoorState; } public function lock() { return new LockedDoorState; } }
236. class ClosedDoorState extends AbstractDoorState { public function open() { return new OpenDoorState; } public function lock() { return new LockedDoorState; } }
237. class ClosedDoorState extends AbstractDoorState { public function open() { return new OpenDoorState; } public function lock() { return new LockedDoorState; } }
238. class ClosedDoorState extends AbstractDoorState { public function open() { return new OpenDoorState; } public function lock() { return new LockedDoorState; } }
241. • Context Object maintains a reference to the Stateful Object.
242. • Context Object maintains a reference to the Stateful Object. • States & Transitions are mapped and maintained by the Context Object.
243. • Context Object maintains a reference to the Stateful Object. • States & Transitions are mapped and maintained by the Context Object. • State Transitions are introduced externally rather than in response to Triggers.
244. • Context Object maintains a reference to the Stateful Object. • States & Transitions are mapped and maintained by the Context Object. • State Transitions are introduced externally rather than in response to Triggers. • The Context Object determines if Transitions are allowed.
246. github.com/yohang/finite
249. class Document implements Finite\StatefulInterface { private $state; public function getFiniteState() { return $this->state; } public function setFiniteState($state) { $this->state = $state; } }
250. class Document implements Finite\StatefulInterface { private $state; public function getFiniteState() { return $this->state; } public function setFiniteState($state) { $this->state = $state; } }
251. class Document implements Finite\StatefulInterface { private $state; public function getFiniteState() { return $this->state; } public function setFiniteState($state) { $this->state = $state; } }
252. class Document implements Finite\StatefulInterface { private $state; public function getFiniteState() { return $this->state; } public function setFiniteState($state) { $this->state = $state; } }
253. class Document implements Finite\StatefulInterface { private $state; public function getFiniteState() { return $this->state; } public function setFiniteState($state) { $this->state = $state; } }
254. class Document implements Finite\StatefulInterface { private $state; public function getFiniteState() { return $this->state; } public function setFiniteState($state) { $this->state = $state; } }
256. $stateMap = [ 'class' => 'Document', 'states' => [ 'draft' => ['type' => 'initial', 'properties' => []], 'proposed' => ['type' => 'normal', 'properties' => []], 'accepted' => ['type' => 'final', 'properties' => []], 'refused' => ['type' => 'final', 'properties' => []], ], 'transitions' => [ 'propose' => ['from' => ['draft'], 'to' => 'proposed'], 'accept' => ['from' => ['proposed'], 'to' => 'accepted'], 'refuse' => ['from' => ['proposed'], 'to' => 'refused'], ] ]; $stateMachine = new Finite\StateMachine\StateMachine; $loader->load(new Finite\Loader\ArrayLoader($stateMap)); $stateMachine->setObject(new Document); $stateMachine->initialize();
257. $stateMap = [ 'class' => 'Document', 'states' => [ 'draft' => ['type' => 'initial', 'properties' => []], 'proposed' => ['type' => 'normal', 'properties' => []], 'accepted' => ['type' => 'final', 'properties' => []], 'refused' => ['type' => 'final', 'properties' => []], ], 'transitions' => [ 'propose' => ['from' => ['draft'], 'to' => 'proposed'], 'accept' => ['from' => ['proposed'], 'to' => 'accepted'], 'refuse' => ['from' => ['proposed'], 'to' => 'refused'], ] ]; $stateMachine = new Finite\StateMachine\StateMachine; $loader->load(new Finite\Loader\ArrayLoader($stateMap)); $stateMachine->setObject(new Document); $stateMachine->initialize();
258. $stateMap = [ 'class' => 'Document', 'states' => [ 'draft' => ['type' => 'initial', 'properties' => []], 'proposed' => ['type' => 'normal', 'properties' => []], 'accepted' => ['type' => 'final', 'properties' => []], 'refused' => ['type' => 'final', 'properties' => []], ], 'transitions' => [ 'propose' => ['from' => ['draft'], 'to' => 'proposed'], 'accept' => ['from' => ['proposed'], 'to' => 'accepted'], 'refuse' => ['from' => ['proposed'], 'to' => 'refused'], ] ]; $stateMachine = new Finite\StateMachine\StateMachine; $loader->load(new Finite\Loader\ArrayLoader($stateMap)); $stateMachine->setObject(new Document); $stateMachine->initialize();
259. $stateMap = [ 'class' => 'Document', 'states' => [ 'draft' => ['type' => 'initial', 'properties' => []], 'proposed' => ['type' => 'normal', 'properties' => []], 'accepted' => ['type' => 'final', 'properties' => []], 'refused' => ['type' => 'final', 'properties' => []], ], 'transitions' => [ 'propose' => ['from' => ['draft'], 'to' => 'proposed'], 'accept' => ['from' => ['proposed'], 'to' => 'accepted'], 'refuse' => ['from' => ['proposed'], 'to' => 'refused'], ] ]; $stateMachine = new Finite\StateMachine\StateMachine; $loader->load(new Finite\Loader\ArrayLoader($stateMap)); $stateMachine->setObject(new Document); $stateMachine->initialize();
260. $stateMap = [ 'class' => 'Document', 'states' => [ 'draft' => ['type' => 'initial', 'properties' => []], 'proposed' => ['type' => 'normal', 'properties' => []], 'accepted' => ['type' => 'final', 'properties' => []], 'refused' => ['type' => 'final', 'properties' => []], ], 'transitions' => [ 'propose' => ['from' => ['draft'], 'to' => 'proposed'], 'accept' => ['from' => ['proposed'], 'to' => 'accepted'], 'refuse' => ['from' => ['proposed'], 'to' => 'refused'], ] ]; $stateMachine = new Finite\StateMachine\StateMachine; $loader->load(new Finite\Loader\ArrayLoader($stateMap)); $stateMachine->setObject(new Document); $stateMachine->initialize();
261. $stateMap = [ 'class' => 'Document', 'states' => [ 'draft' => ['type' => 'initial', 'properties' => []], 'proposed' => ['type' => 'normal', 'properties' => []], 'accepted' => ['type' => 'final', 'properties' => []], 'refused' => ['type' => 'final', 'properties' => []], ], 'transitions' => [ 'propose' => ['from' => ['draft'], 'to' => 'proposed'], 'accept' => ['from' => ['proposed'], 'to' => 'accepted'], 'refuse' => ['from' => ['proposed'], 'to' => 'refused'], ] ]; $stateMachine = new Finite\StateMachine\StateMachine; $loader->load(new Finite\Loader\ArrayLoader($stateMap)); $stateMachine->setObject(new Document); $stateMachine->initialize();
262. $stateMap = [ 'class' => 'Document', 'states' => [ 'draft' => ['type' => 'initial', 'properties' => []], 'proposed' => ['type' => 'normal', 'properties' => []], 'accepted' => ['type' => 'final', 'properties' => []], 'refused' => ['type' => 'final', 'properties' => []], ], 'transitions' => [ 'propose' => ['from' => ['draft'], 'to' => 'proposed'], 'accept' => ['from' => ['proposed'], 'to' => 'accepted'], 'refuse' => ['from' => ['proposed'], 'to' => 'refused'], ] ]; $stateMachine = new Finite\StateMachine\StateMachine; $loader->load(new Finite\Loader\ArrayLoader($stateMap)); $stateMachine->setObject(new Document); $stateMachine->initialize();
264. echo $stateMachine->getCurrentState(); // => "draft“ var_dump($stateMachine->can('accept')); // => bool(false) var_dump($stateMachine->can('propose')); // => bool(true) $stateMachine->apply('propose'); echo $stateMachine->getCurrentState(); // => "proposed"
265. echo $stateMachine->getCurrentState(); // => "draft“ var_dump($stateMachine->can('accept')); // => bool(false) var_dump($stateMachine->can('propose')); // => bool(true) $stateMachine->apply('propose'); echo $stateMachine->getCurrentState(); // => "proposed"
266. echo $stateMachine->getCurrentState(); // => "draft“ var_dump($stateMachine->can('accept')); // => bool(false) var_dump($stateMachine->can('propose')); // => bool(true) $stateMachine->apply('propose'); echo $stateMachine->getCurrentState(); // => "proposed"
267. echo $stateMachine->getCurrentState(); // => "draft“ var_dump($stateMachine->can('accept')); // => bool(false) var_dump($stateMachine->can('propose')); // => bool(true) $stateMachine->apply('propose'); echo $stateMachine->getCurrentState(); // => "proposed"
268. echo $stateMachine->getCurrentState(); // => "draft“ var_dump($stateMachine->can('accept')); // => bool(false) var_dump($stateMachine->can('propose')); // => bool(true) $stateMachine->apply('propose'); echo $stateMachine->getCurrentState(); // => "proposed"
271. Is Your State & Transition Graph
272. • exceptionally complex? Is Your State & Transition Graph
273. • exceptionally complex? • subject to frequent change? Is Your State & Transition Graph
274. • exceptionally complex? • subject to frequent change? • externally configurable? Is Your State & Transition Graph
276. Follow Roughly the Same Design
277. Follow Roughly the Same Design • Wrapper
278. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee”
279. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee” • Delegation
280. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee” • Delegation Solve the Same Problems
281. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee” • Delegation Solve the Same Problems • Allow object to alter behavior when internal state changes
282. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee” • Delegation Solve the Same Problems • Allow object to alter behavior when internal state changes Provide the Same Benefits
283. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee” • Delegation Solve the Same Problems • Allow object to alter behavior when internal state changes Provide the Same Benefits • Increased Flexibility
284. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee” • Delegation Solve the Same Problems • Allow object to alter behavior when internal state changes Provide the Same Benefits • Increased Flexibility • Increased Control
285. Follow Roughly the Same Design • Wrapper • Polymorphic “Wrappee” • Delegation Solve the Same Problems • Allow object to alter behavior when internal state changes Provide the Same Benefits • Increased Flexibility • Increased Control • Increased Visibility
287. Fear Not the Machine of State!