Allow the transitions / known states for an event to be reset

CHANGELOG.md

@@ -1,5 +1,6 @@
 # master
 
+* Allow the transitions / known states for an event to be reset
 * Add fire_#{name}_event instance method for firing an arbitrary event on a state machine
 * Improve InvalidTransition exception messages to include the failure reason(s) in ORM integrations
 * Don't allow around_transitions to attempt to be called in multiple execution contexts when run in jruby

lib/state_machine/event.rb

@@ -55,8 +55,7 @@ def initialize(machine, name, options = {}) #:nodoc:
       @name = name
       @qualified_name = machine.namespace ? :"#{name}_#{machine.namespace}" : name
       @human_name = options[:human_name] || @name.to_s.tr('_', ' ')
-      @branches = []
-      @known_states = []
+      reset
 
       # Output a warning if another event has a conflicting qualified name
       if conflict = machine.owner_class.state_machines.detect {|name, other_machine| other_machine != @machine && other_machine.events[qualified_name, :qualified_name]}
@@ -186,6 +185,15 @@ def on_failure(object)
       Transition.new(object, machine, name, state.name, state.name).run_callbacks(:before => false)
     end
 
+    # Resets back to the initial state of the event, with no branches / known
+    # states associated.  This allows you to redefine an event in situations
+    # where you either are re-using an existing state machine implementation
+    # or are subclassing machines.
+    def reset
+      @branches = []
+      @known_states = []
+    end
+
     # Draws a representation of this event on the given graph.  This will
     # create 1 or more edges on the graph for each branch (i.e. transition)
     # configured.

test/unit/event_test.rb

@@ -474,6 +474,11 @@ def test_should_include_new_transition_states_after_calling_known_states
     assert_equal [:parked, :idling, :first_gear, :stalled], @event.known_states
   end
 
+  def test_should_clear_known_states_on_reset
+    @event.reset
+    assert_equal [], @event.known_states
+  end
+
   def test_should_use_pretty_inspect
     assert_match "#<StateMachine::Event name=:ignite transitions=[:parked => :idling, :first_gear => :idling]>", @event.inspect
   end
@@ -690,6 +695,11 @@ def test_should_not_invalidate_the_state
     assert_equal [], @object.errors
   end
 
+  def test_should_not_be_able_to_fire_on_reset
+    @event.reset
+    assert !@event.can_fire?(@object)
+  end
+
   def teardown
     StateMachine::Integrations.send(:remove_const, 'Custom')
   end