Add Access.on and Access.on_changed

lib/qml/access.rb

@@ -13,10 +13,29 @@ class PropertyInfo
     # @api private
     class SignalInfo
       attr_accessor :params
+      attr_accessor :listeners
+
+      def initialize
+        @listeners = []
+      end
     end
 
     def initialize(*args, &block)
-      self.class.property_infos.each_value.map(&:initializer).compact.each(&:call)
+
+      self.class.property_infos.each do |name, info|
+        if info.initializer
+          self.__send__ :"#{name}=", instance_eval(&info.initializer)
+        end
+      end
+
+      self.class.signal_infos.each do |name, info|
+        __send__(name).connect do |*args|
+          info.listeners.each do |listener|
+            instance_eval(&listener)
+          end
+        end
+      end
+
       super
     end
 
@@ -108,6 +127,18 @@ def property_infos(include_super = true)
         end
       end
 
+      def on(signal, &block)
+        info = signal_infos(false)[signal.to_sym] or fail AccessError, "no signal `#{signal}` found"
+        info.listeners << block
+        block
+      end
+
+      def on_changed(property, &block)
+        on(:"#{property}_changed", &block)
+      end
+
+      private :on, :on_changed
+
       # Registers the class as a QML type.
       # @param opts [Hash]
       # @option opts [String] :under the namespece which encapsulates the exported QML type. If not specified, automatically inferred from the module nesting of the class.

spec/qml/access_spec.rb

@@ -5,6 +5,42 @@
   let(:component) { QML::Component.new data: data }
   let(:root) { component.create }
 
+  describe 'signal listener' do
+    let(:button_class) do
+      Class.new do
+        include QML::Access
+        signal :pressed
+        property(:is_pressed) { false }
+        property :id
+        property(:is_id_changed) { false }
+
+        on :pressed do |pos|
+          self.is_pressed = true
+        end
+        on_changed :id do
+          self.is_id_changed = true
+        end
+      end
+    end
+    let(:button) { button_class.new }
+
+    describe '.on' do
+      it 'registers a signal listener' do
+        expect(button.is_pressed).to eq(false)
+        button.pressed.emit
+        expect(button.is_pressed).to eq(true)
+      end
+    end
+
+    describe '.on_changed' do
+      it 'registers a property change listener' do
+        expect(button.is_id_changed).to eq(false)
+        button.id = "foo"
+        expect(button.is_id_changed).to eq(true)
+      end
+    end
+  end
+
   describe 'property' do
     it 'is converted to JS objects through #to_qml' do
       example = AccessExample.new