Bring in transition guards

lib/aasm.rb

@@ -31,7 +31,7 @@ module AASM
 
       define_method("#{name.to_s}!") do
         new_state = self.class.aasm_events[name].fire(self)
-        self.aasm_current_state = new_state
+        self.aasm_current_state = new_state unless new_state.nil?
         nil
       end
     end

lib/event.rb

@@ -13,11 +13,16 @@ module AASM
 
       def fire(obj)
         transitions = @transitions.select { |t| t.from == obj.aasm_current_state }
-        if transitions.size == 0
-          raise AASM::InvalidTransition
-        else
-          transitions.first.to
+        raise AASM::InvalidTransition if transitions.size == 0
+
+        next_state = nil
+        transitions.each do |transition|
+          if transition.perform(obj)
+            next_state = transition.to
+            break
+          end
         end
+        next_state
       end
 
       private

lib/state_transition.rb

@@ -8,6 +8,17 @@ module AASM
         @opts = opts
       end
 
+      def perform(obj)
+        case @guard
+        when Symbol, String
+          obj.send(@guard)
+        when Proc
+          @guard.call(obj)
+        else
+          true
+        end
+      end
+      
       def ==(obj)
         @from == obj.from && @to == obj.to
       end

spec/state_transition_spec.rb

@@ -44,3 +44,41 @@ describe AASM::SupportingClasses::StateTransition do
   end
 end
 
+describe AASM::SupportingClasses::StateTransition, '- when performing guard checks' do
+  it 'should return true of there is no guard' do
+    opts = {:from => 'foo', :to => 'bar'}
+    st = AASM::SupportingClasses::StateTransition.new(opts)
+
+    st.perform(nil).should be_true
+  end
+
+  it 'should call the method on the object if guard is a symbol' do
+    opts = {:from => 'foo', :to => 'bar', :guard => :test}
+    st = AASM::SupportingClasses::StateTransition.new(opts)
+
+    obj = mock('object')
+    obj.should_receive(:test)
+    
+    st.perform(obj)
+  end
+
+  it 'should call the method on the object if guard is a string' do
+    opts = {:from => 'foo', :to => 'bar', :guard => 'test'}
+    st = AASM::SupportingClasses::StateTransition.new(opts)
+
+    obj = mock('object')
+    obj.should_receive(:test)
+    
+    st.perform(obj)
+  end
+
+  it 'should call the proc passing the object if the guard is a proc' do
+    opts = {:from => 'foo', :to => 'bar', :guard => Proc.new {|o| o.test}}
+    st = AASM::SupportingClasses::StateTransition.new(opts)
+
+    obj = mock('object')
+    obj.should_receive(:test)
+
+    st.perform(obj)
+  end
+end