CakePHP Finite State Machine Behavior

A basic finite state machine behavior for CakePHP 2.x. A version for CakePHP 1 can be found in the branch cakephp1.

Describe a model's states and the events that cause transitions between them, then trigger these events to change your model to a new state.

Installation

If you're using composer then just add the following to your require block.

	"burriko/cake-state-machine": "2.0.*@dev"

If you're not, then clone/copy the contents of this directory to app/Plugins/CakeStateMachine.

Configure

1. Add the following line to your app/Config/bootstrap.php.

    CakePlugin::load('CakeStateMachine');
   

2. In your model add:

    public $actsAs = array('CakeStateMachine.StateMachine');
   

3. Create a new database table to store the states using the following schema, adjusting the table name and foreign key to match your model. For example, if you are adding states to a model name Placement you would use the following.

    CREATE TABLE `placement_states` (
      `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
      `placement_id` int(11) unsigned NOT NULL,
      `state` varchar(50) NOT NULL DEFAULT '',
      `created` datetime NOT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
   

4. Add a new varchar field to your model's table called 'state'.

    ALTER TABLE `placements` ADD `state` VARCHAR(50);
   

Usage

1. In your model describe the states and transitions you need like so.

    public $states = array('state' => array('event' => 'new_state'));
   

   Here's an example.

    public $states = array(
      'advertised' => array(
        'select_appropriate_applicants' => 'shortlisted',
        'no_appropriate_applicants' => 'unplaced'
      ),
      'shortlisted' => array(
        'select_for_interview' => 'interviews',
        'no_appropriate_applicants' => 'unplaced'
      ),
      'interviews' => array(
        'select_successful_candidate' => 'placed',
        'no_appropriate_applicants' => 'unplaced'
      ),
      'placed' => array(
        'placement_complete' => 'complete',
        'problem_with_placement' => 'unplaced'
      ),
      'unplaced' => array(
        'readvertise' => 'advertised'
      ),
      'complete'
    );
   

2. When a new record is created by that model it will be assigned the first state in the list as it's initial state.

3. To transition to a new state call pass the name of an event to the transition() method.

    $this->Model->transition('event');
   

   In this example if the Placement model was in the 'interviews' state it would transition to the 'placed' state.

    $this->Placement->transition('select_successful_candidate');
   

4. Every state change is recorded in the database. Every model that uses the StateMachine behavior will have an appropriate state model named ModelnameState. The model is related to this with a hasMany relationship. You can therefore use this model to look up state changes however you want.

    $this->Placement->PlacementState->findByPlacementId($placement_id);
   

   You can also find the current state of a model from the getCurrentState() method.

    // set model id if not already set
    $this->Placement->id = $placement_id;
    $this->Placement->getCurrentState(); // returns 'placed'
   

Notes

• The current state of a record is also stored in the 'state' column of the model. This is to make it easier when querying the model by state.

• A callback method is supported for state changes. This should be titled _onState(). For example, to run a method when the model changes to a state named 'placed' add the following method to your model.

    public function _onStatePlaced() {}
  

• You can check whether a state is currently set by calling is<NameOfState>(). For example to check whether a Placement record is currently set to shortlisted call the following.

    $this->Placement->isShortlisted();