delegating ControllerResource find to model adapter, uses 'get' for DataMapper - closes #373

lib/cancan/controller_resource.rb

@@ -107,11 +107,15 @@ module CanCan
             resource_base.send(@options[:find_by], id_param)
           end
         else
-          resource_base.find(id_param)
+          adapter.find(resource_base, id_param)
         end
       end
     end
 
+    def adapter
+      ModelAdapters::AbstractAdapter.adapter_class(resource_class)
+    end
+
     def authorization_action
       parent? ? :show : @params[:action].to_sym
     end

lib/cancan/model_adapters/abstract_adapter.rb

@@ -15,6 +15,11 @@ module CanCan
         false # override in subclass
       end
 
+      # Override if you need custom find behavior
+      def self.find(model_class, id)
+        model_class.find(id)
+      end
+
       # Used to determine if this model adapter will override the matching behavior for a hash of conditions.
       # If this returns true then matches_conditions_hash? will be called. See Rule#matches_conditions_hash
       def self.override_conditions_hash_matching?(subject, conditions)

lib/cancan/model_adapters/data_mapper_adapter.rb

@@ -5,6 +5,10 @@ module CanCan
         model_class <= DataMapper::Resource
       end
 
+      def self.find(model_class, id)
+        model_class.get(id)
+      end
+
       def self.override_conditions_hash_matching?(subject, conditions)
         conditions.any? { |k,v| !k.kind_of?(Symbol) }
       end