Merge pull request #6 from stekker/message-handler-reloading

Make `MessageHandler` work with Rails code reloading

lib/s2/message_handler.rb

@@ -3,22 +3,30 @@ module MessageHandler
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :handlers, default: {}
+      class_attribute :message_handlers, instance_writer: false, default: {}
     end
 
     class_methods do
-      def on(message_type, &handler)
-        if handlers.has_key?(message_type)
-          raise ArgumentError, "A handler for message class '#{message_type}' already exists"
+      def on(message_class, &handler)
+        if find_handler(message_class)
+          raise ArgumentError, "A handler for message class '#{message_class}' is already defined"
         end
 
-        handlers[message_type] = handler
+        self.message_handlers = message_handlers.merge(key(message_class) => handler)
+      end
+
+      def key(message_class)
+        message_class
+      end
+
+      def find_handler(message_class)
+        message_handlers[key(message_class)]
       end
     end
 
     def handle_message(message)
-      handler = self.class.handlers[message.class]
-      raise ArgumentError, "No handler found for message class '#{message.class}'" if handler.nil?
+      handler = self.class.find_handler(message.class)
+      raise ArgumentError, "No handler defined for message class '#{message.class}'" if handler.nil?
 
       instance_exec(message, &handler)
     end

spec/lib/s2/message_handler_spec.rb

@@ -22,6 +22,39 @@ def initialize
       expect { handler.handle_message(message) }.to change { handler.received_messages }.to([message])
     end
 
+    it "works with inheritance" do
+      some_message_class = Class.new
+      other_message_class = Class.new
+      base_handler_class = Class.new do
+        include S2::MessageHandler
+
+        attr_reader :received_messages
+
+        def initialize
+          @received_messages = []
+        end
+
+        on some_message_class do |message|
+          @received_messages << message
+        end
+      end
+
+      sub_handler_class = Class.new(base_handler_class) do
+        on other_message_class do |message|
+          @received_messages << message
+        end
+      end
+
+      handler = sub_handler_class.new
+      some_message = some_message_class.new
+      other_message = other_message_class.new
+
+      expect { handler.handle_message(some_message) }
+        .to change { handler.received_messages }.to([some_message])
+      expect { handler.handle_message(other_message) }
+        .to change { handler.received_messages }.to([some_message, other_message])
+    end
+
     it "raises when a duplicate handler is defined" do
       message_class = Class.new
       stub_const("TestNamespace::TestMessage", message_class)
@@ -38,7 +71,10 @@ def initialize
             # no-op
           end
         end
-      end.to raise_error(ArgumentError, "A handler for message class 'TestNamespace::TestMessage' already exists")
+      end.to raise_error(
+        ArgumentError,
+        "A handler for message class 'TestNamespace::TestMessage' is already defined",
+      )
     end
 
     it "raises when no handler could be found for the given message" do
@@ -51,7 +87,7 @@ def initialize
       message = message_class.new
 
       expect { handler.handle_message(message) }
-        .to raise_error(ArgumentError, "No handler found for message class '#{message.class}'")
+        .to raise_error(ArgumentError, "No handler defined for message class '#{message.class}'")
     end
   end
 end