Simple Finite State Machine

dev-master 2014-06-10 09:05 UTC

This package is not auto-updated.

Last update: 2021-11-27 01:07:56 UTC


README

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THis library provides a simple integrated Finite State Machine. The state machine consts of States/Transitions/Triggers.

  1. States

States define the...states that your machine can be in at any given point during the process. States are connected by transitions.

$stateCreated = new State('created', StateInterface::TYPE_INITIAL);
$stateImported = new State('imported');
$stateLive = new State('imported', StateInterface::TYPE_FINAL);

State types include TYPE_INITIAL, TYPE_INTERMEDIATE, TYPE_FINAL.

Actions

States can contain actions. Actions are set tasks that need to be performed in order to successfully transition. Like saying, "when a payment goes into a pending state, we need to notify a support consultant.".

$stateImported = new State('imported');
$stateImported->addAction(new NotifyAction());
$stateImported->addAction(new TwitterAction());
  1. Transitions

Transitions are logical links (paths) between different states. Transitions can also have a transfer condition. Transfer conditions need to evaluate to true to transition to a new state. Transitions are constructed by specifying it's initial state and the state to which it needs to transfer.

$transitionCreatedImported = new Transition($stateCreated, $stateImported);
$transitionImportedLive = new Transition($stateImported, $stateLive);

Conditions

A transition can have an optional condition. This condition must evaluate to true. Conditions can easily be recycled by different states.

class ImportPermissions implements \FSM\StateMachine\Condition\ConditionInterface
{
    public function check()
    {
        return true; // Return true/false depending on the outcome of your condition
    }
}

$transitionCreatedImported = new Transition($stateCreated, $stateImported);
$transitionCreatedImported->addCondition(new ImportPermissions());

$transitionImportedLive = new Transition($stateImported, $stateLive);
  1. Triggers

Triggers are certain events that can be fired that will attempt to push the StateMachine forward. Triggers can be associated with a series of different transitions and will automatically determine which transition path to follow.

$stateMachine->addTrigger('triggerName', array($transitionCreatedImported, $transitionImportedLive));
  1. Usage Example

Putting it all together, the state machine will look something like this:

// Set up a condition
class ImportPermissions implements \FSM\StateMachine\Condition\ConditionInterface
{
    public function check()
    {
        return true; // Return true/false depending on the outcome of your condition
    }
}

// Set up a machine
class ImportMachine extends \FSM\StateMachine\StateMachine
{
    public function __construct($name)
    {
        // Potentially inject some custom dependencies?
        parent::__construct($name);
    }

    protected function configureMachine()
    {
        $stateCreated = new State('created', StateInterface::TYPE_INITIAL);
        $stateImported = new State('imported');
        $stateLive = new State('imported', StateInterface::TYPE_FINAL);

        $transitionCreatedImported = new Transition($stateCreated, $stateImported);
        $transitionCreatedImported->addCondition(new ImportPermissions());

        $transitionImportedLive = new Transition($stateImported, $stateLive);

        // Add the supported machine transitions
        $this->addTransition($transitionCreatedImported);
        $this->addTransition($transitionImportedLive);

        // Add machine triggers
        $this->addTrigger('import', array($transitionCreatedImported, $transitionImportedLive));
        $this->addTrigger('live', array($transitionImportedLive));

        // The initial state can be determined by external dependencies
        // if required
        $this->setCurrentState('created');
    }
}

$machine = new ImportMachine();

echo $machine->getCurrentState(); // echo 'created'

// Trigger machine import
$machine->trigger('import');

echo $machine->getCurrentState(); // echo 'imported' (update the ImportPermissions return to false will echo 'created')

// Trigger machine 'mark as live'
$machine->trigger('live');

echo $machine->getCurrentState(); // echo 'live'

Since the "import" trigger contains both the import and live transition. This trigger can be "deep resolved". This means that it can go straight from importing to making it live. To enable deep resolution you can pass $machine->trigger('import', true);

  1. More Examples

For a more in depth example and a visual representation of a state graph. You can view tests/FSM/StateMachine/Stage/Graph.php in your browser. You need to optionally download the GraphViz library in order to generate a more detailed image.