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

	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

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.

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.

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.