New workflow definition cleanly undefines the old convinience methods, s. also #92, #69

geekq · geekq · commit ff6752f950d9 · 2013-08-26T13:56:01.000+02:00
* works on both subclassing and dynamic workflow spec assignment
* solving problems caused by metaprogramming with even more metaprogramming ;-)
diff --git a/lib/workflow.rb b/lib/workflow.rb
@@ -25,11 +25,28 @@ def workflow(&specification)
 
     private
 
+    # Creates the convinience methods like `my_transition!`
     def assign_workflow(specification_object)
-      # TODO Ensure assign_workflow can be only called once
-      #
-      # creates the convinence methods, note: there is currently no way
-      # to reassign different workflow, undefining created methods
+
+      # Merging two workflow specifications can **not** be done automically, so
+      # just make the latest specification win. Same for inheritance -
+      # definition in the subclass wins.
+      if respond_to? :inherited_workflow_spec # undefine methods defined by the old workflow_spec
+        inherited_workflow_spec.states.values.each do |state|
+          state_name = state.name
+          module_eval do
+            undef_method "#{state_name}?"
+          end
+
+          state.events.values.each do |event|
+            event_name = event.name
+            module_eval do
+              undef_method "#{event_name}!".to_sym
+              undef_method "can_#{event_name}?"
+            end
+          end
+        end
+      end
 
       @workflow_spec = specification_object
       @workflow_spec.states.values.each do |state|
@@ -230,6 +247,19 @@ def persist_workflow_state(new_value)
 
   def self.included(klass)
     klass.send :include, InstanceMethods
+
+    # backup the parent workflow spec, making accessible through #inherited_workflow_spec
+    if klass.superclass.respond_to?(:workflow_spec, true)
+      klass.module_eval do
+        # see http://stackoverflow.com/a/2495650/111995 for implementation explanation
+        pro = Proc.new { klass.superclass.workflow_spec }
+        singleton_class = class << self; self; end
+        singleton_class.send(:define_method, :inherited_workflow_spec) do
+          pro.call
+        end
+      end
+    end
+
     klass.extend ClassMethods
 
     if Object.const_defined?(:ActiveRecord)
diff --git a/test/inheritance_test.rb b/test/inheritance_test.rb
@@ -0,0 +1,54 @@
+require File.join(File.dirname(__FILE__), 'test_helper')
+require 'workflow'
+class InheritanceTest < ActiveRecordTestCase
+
+  test '#69 inheritance' do
+    class Animal
+      include Workflow
+
+      workflow do
+
+        state :conceived do
+          event :birth, :transition_to => :born
+        end
+
+        state :born do
+
+        end
+      end
+    end
+
+    class Cat < Animal
+      include Workflow
+      workflow do
+
+        state :upset do
+          event :scratch, :transition_to => :hiding
+        end
+
+        state :hiding do
+
+        end
+      end
+    end
+
+    assert_equal [:born, :conceived] , Animal.workflow_spec.states.keys.sort
+    assert_equal [:hiding, :upset], Cat.workflow_spec.states.keys.sort, "Workflow definitions are not inherited"
+
+    animal = Animal.new
+    cat = Cat.new
+
+    animal.birth!
+
+    assert_raise NoMethodError, 'Methods defined by the old workflow spec should have be gone away' do
+      cat.birth!
+    end
+
+    assert_equal [:birth!, :halt!, :process_event!], bang_methods(animal)
+    assert_equal [:halt!, :process_event!, :scratch!], bang_methods(cat)
+  end
+
+  def bang_methods(obj)
+    (obj.public_methods-Object.public_methods).select {|m| m =~ /!$/}.sort
+  end
+end
