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.

Transcript

1. Fear Not
   the Machine
   of State!
   

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3. Yitzchok
   Willroth
   

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4. Yitzchok
   Willroth
   

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5. Yitzchok
   Willroth
   @coderabbi
   

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6. Yitzchok
   Willroth
   @coderabbi
   

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7. Yitzchok
   Willroth
   @coderabbi
   

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19. State Pattern
    

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20. State Pattern
    • Behavioral Pattern
    

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21. State Pattern
    • Behavioral Pattern
    • Allows an object to alter its behavior when its
    internal state changes, giving the appearance of
    changing class.
    

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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.
    

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35. IDENTIFY
    STATES
    

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37. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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38. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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40. IDENTIFY
    TRANSITIONS
    

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42. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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43. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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44. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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45. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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46. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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47. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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48. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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49. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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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;
    }
    }
    

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64. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    

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65. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    

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66. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    

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67. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    

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68. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    

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69. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    

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70. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    

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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 ...
    

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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 ...
    

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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 ...
    

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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 ...
    

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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 ...
    

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80. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Coin
    Refund
    

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81. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Coin
    Refund
    Violation
    

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82. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass Coin
    Refund
    Violation
    

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83. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    

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84. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    

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85. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    

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86. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    

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87. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    Lock
    

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88. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    Lock
    

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89. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    Lock
    Coin
    

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90. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    

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91. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    

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92. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    Pass
    

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93. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    Pass
    

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94. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Reset
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    Pass
    

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95. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Reset
    ResetAlarm
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    Pass
    

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96. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Reset
    ResetAlarm
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    Pass
    

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97. View Slide

98. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Reset
    ResetAlarm
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    Pass
    

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99. Locked
    Coin
    Unlock
    Pass
    Lock
    Unlocked
    Pass
    Alarm
    Coin
    Refund
    Violation
    Reset
    ResetAlarm
    Ready
    ResetAlarm
    Lock
    Coin
    Refund
    Pass
    

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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
     

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101. Locked
     Coin
     Unlock
     Pass
     Lock
     Unlocked
     Pass
     Alarm
     Coin
     Refund
     Violation
     Reset
     ResetAlarm
     Ready
     ResetAlarm
     Lock
     NORMAL MODE
     Coin
     Refund
     Pass
     

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102. Locked
     Coin
     Unlock
     Pass
     Lock
     Unlocked
     Pass
     Alarm
     Coin
     Refund
     Violation
     Reset
     ResetAlarm
     Ready
     ResetAlarm
     Lock
     NORMAL MODE
     DIAGNOSTIC MODE
     Coin
     Refund
     Pass
     

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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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104. 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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105. View Slide

106. Locked
     Coin
     Unlock
     Pass
     Lock
     Unlocked
     Pass
     Alarm
     Coin
     Refund
     

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107. View Slide

108. View Slide

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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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122. View Slide

123. abstract class TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     //empty implementation
     }
     public function coin(Turnstile $turnstile)
     {
     //empty implementation
     }
     }
     

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124. abstract class TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     //empty implementation
     }
     public function coin(Turnstile $turnstile)
     {
     //empty implementation
     }
     }
     

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125. abstract class TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     //empty implementation
     }
     public function coin(Turnstile $turnstile)
     {
     //empty implementation
     }
     }
     

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126. abstract class TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     //empty implementation
     }
     public function coin(Turnstile $turnstile)
     {
     //empty implementation
     }
     }
     

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127. abstract class TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     //empty implementation
     }
     public function coin(Turnstile $turnstile)
     {
     //empty implementation
     }
     }
     

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128. View Slide

129. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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130. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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131. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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132. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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133. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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134. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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135. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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136. class LockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->alarm->sound();
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->unlockedState);
     }
     }
     

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137. View Slide

138. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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139. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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140. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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141. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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142. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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143. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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144. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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145. class unlockedTurnstileState extends TurnstileState
     {
     public function pass(Turnstile $turnstile)
     {
     $turnstile->setState($turnstile->lockedState);
     }
     public function coin(Turnstile $turnstile)
     {
     $turnstile->coinVendor->refund();
     }
     }
     

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146. View Slide

147. View Slide

148. Locked
     Coin
     Unlock
     Pass
     Lock
     Unlocked
     Pass
     Alarm
     Coin
     Refund
     

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149. Locked
     Coin
     Unlock
     Pass
     Lock
     Unlocked
     Pass
     Alarm
     Coin
     Refund
     Violation
     Reset
     ResetAlarm
     Ready
     ResetAlarm
     Lock
     Coin
     Refund
     Pass
     

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150. View Slide

151. View Slide

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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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159. View Slide

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
     }
     }
     

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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
     }
     }
     

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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
     }
     }
     

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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
     }
     }
     

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164. View Slide

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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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171. View Slide

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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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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);
     }
     }
     

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176. View Slide

177. View Slide

178. Locked
     Coin
     Unlock
     Pass
     Lock
     Unlocked
     Pass
     Alarm
     Coin
     Refund
     Violation
     Reset
     ResetAlarm
     Ready
     ResetAlarm
     Lock
     Coin
     Refund
     Pass
     

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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
     

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180. View Slide

181. Extend the public API of the
     “context” & Abstract “state” classes
     To include new event triggers
     

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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
     

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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
     

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184. View Slide

185. Flexibility
     

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186. CONTROL
     

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187. VISIBILITY
     

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188. View Slide

189. View Slide

190. View Slide

191. View Slide

192. View Slide

193. View Slide

194. • State Variables
     

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195. • State Variables
     • $status
     

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196. • State Variables
     • $status
     • $state
     

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197. • State Variables
     • $status
     • $state
     • Boolean Driven Development
     

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198. • State Variables
     • $status
     • $state
     • Boolean Driven Development
     • $active, $published
     

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199. • State Variables
     • $status
     • $state
     • Boolean Driven Development
     • $active, $published
     • isActive(), isPublished()
     

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200. • State Variables
     • $status
     • $state
     • Boolean Driven Development
     • $active, $published
     • isActive(), isPublished()
     • Nullable Timestamps
     

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201. • State Variables
     • $status
     • $state
     • Boolean Driven Development
     • $active, $published
     • isActive(), isPublished()
     • Nullable Timestamps
     • Multipart Conditionals or Switches
     

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202. View Slide

203. View Slide

204. View Slide

205. View Slide

206. View Slide

207. View Slide

208. View Slide

209. View Slide

210. View Slide

211. View Slide

212. View Slide

213. View Slide

214. View Slide

215. View Slide

216. View Slide

217. github.com/sebastianbergmann/state
     

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218. View Slide

219. View Slide

220. 
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     

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221. View Slide

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
     

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223. View Slide

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;
     }
     }
     

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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;
     }
     }
     

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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;
     }
     }
     

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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;
     }
     }
     

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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;
     }
     }
     

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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;
     }
     }
     

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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;
     }
     }
     

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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;
     }
     }
     

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232. View Slide

233. class ClosedDoorState extends AbstractDoorState
     {
     public function open()
     {
     return new OpenDoorState;
     }
     public function lock()
     {
     return new LockedDoorState;
     }
     }
     

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234. class ClosedDoorState extends AbstractDoorState
     {
     public function open()
     {
     return new OpenDoorState;
     }
     public function lock()
     {
     return new LockedDoorState;
     }
     }
     

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235. class ClosedDoorState extends AbstractDoorState
     {
     public function open()
     {
     return new OpenDoorState;
     }
     public function lock()
     {
     return new LockedDoorState;
     }
     }
     

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236. class ClosedDoorState extends AbstractDoorState
     {
     public function open()
     {
     return new OpenDoorState;
     }
     public function lock()
     {
     return new LockedDoorState;
     }
     }
     

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237. class ClosedDoorState extends AbstractDoorState
     {
     public function open()
     {
     return new OpenDoorState;
     }
     public function lock()
     {
     return new LockedDoorState;
     }
     }
     

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238. class ClosedDoorState extends AbstractDoorState
     {
     public function open()
     {
     return new OpenDoorState;
     }
     public function lock()
     {
     return new LockedDoorState;
     }
     }
     

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239. View Slide

240. View Slide

241. • Context Object maintains a reference to the Stateful Object.
     

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242. • Context Object maintains a reference to the Stateful Object.
     • States & Transitions are mapped and maintained by the
     Context Object.
     

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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.
     

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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.
     

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245. View Slide

246. github.com/yohang/finite
     

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247. View Slide

248. View Slide

249. class Document implements Finite\StatefulInterface
     {
     private $state;
     public function getFiniteState()
     {
     return $this->state;
     }
     public function setFiniteState($state)
     {
     $this->state = $state;
     }
     }
     

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250. class Document implements Finite\StatefulInterface
     {
     private $state;
     public function getFiniteState()
     {
     return $this->state;
     }
     public function setFiniteState($state)
     {
     $this->state = $state;
     }
     }
     

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251. class Document implements Finite\StatefulInterface
     {
     private $state;
     public function getFiniteState()
     {
     return $this->state;
     }
     public function setFiniteState($state)
     {
     $this->state = $state;
     }
     }
     

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252. class Document implements Finite\StatefulInterface
     {
     private $state;
     public function getFiniteState()
     {
     return $this->state;
     }
     public function setFiniteState($state)
     {
     $this->state = $state;
     }
     }
     

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253. class Document implements Finite\StatefulInterface
     {
     private $state;
     public function getFiniteState()
     {
     return $this->state;
     }
     public function setFiniteState($state)
     {
     $this->state = $state;
     }
     }
     

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254. class Document implements Finite\StatefulInterface
     {
     private $state;
     public function getFiniteState()
     {
     return $this->state;
     }
     public function setFiniteState($state)
     {
     $this->state = $state;
     }
     }
     

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255. View Slide

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();
     

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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();
     

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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();
     

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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();
     

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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();
     

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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();
     

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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();
     

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263. View Slide

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"
     

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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"
     

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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"
     

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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"
     

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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"
     

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269. View Slide

270. View Slide

271. Is Your State & Transition Graph
     

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272. • exceptionally complex?
     Is Your State & Transition Graph
     

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273. • exceptionally complex?
     • subject to frequent change?
     Is Your State & Transition Graph
     

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274. • exceptionally complex?
     • subject to frequent change?
     • externally configurable?
     Is Your State & Transition Graph
     

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275. View Slide

276. Follow Roughly the Same Design
     

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277. Follow Roughly the Same Design
     • Wrapper
     

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278. Follow Roughly the Same Design
     • Wrapper
     • Polymorphic “Wrappee”
     

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279. Follow Roughly the Same Design
     • Wrapper
     • Polymorphic “Wrappee”
     • Delegation
     

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280. Follow Roughly the Same Design
     • Wrapper
     • Polymorphic “Wrappee”
     • Delegation
     Solve the Same Problems
     

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281. Follow Roughly the Same Design
     • Wrapper
     • Polymorphic “Wrappee”
     • Delegation
     Solve the Same Problems
     • Allow object to alter behavior when internal state changes
     

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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
     

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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
     

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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
     

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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
     

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286. View Slide

287. Fear Not
     the Machine
     of State!
     

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