NAME

Class::Workflow::Instance - An instance in a workflow, with state and history.

SYNOPSIS

        package MyInstance;
        use Moose;

        with qw(Class::Workflow::Instance);

        my $instance = MyInstance->new( state => $initial_state );

        my $new_instance = $transition->apply( $instance, @args );

        # $instance is in $initial state, no transitions applied
        # $new_instance may be in another state, $transition has been applied
        # $new_instance->prev == $instance

DESCRIPTION

A workflow instance encapsulates the current state and workflow history on behalf of some parent object that needs state management.

In Class::Workflow these instances are functionally pure, that is they don't change but instead derive their parent copies, and the reference from a given item is to the most recently derived copy.

This eases auditing, reverting, and the writing of transitions.

FIELDS

state: The state this instance is in. Required.
prev: The Class::Workflow::Instance object this object was derived from. Optional.
transition: The transition that created this instance from "prev".

METHODS

derive %fields: Clones the object, setting "prev" to the current object, and shadowing the fields with new values from the key value pair list in the arguments.
clone %fields: The low level clone operation. If you need to override Moose based cloning, because your instance objects are e.g. DBIx::Class objects (see the examples directory), then you would likely want to override this.
See MooseX::Clone for more details.