Move inheritedOfType from Component to Widget so that Switch can use it

packages/flutter/lib/widgets/default_text_style.dart

@@ -19,8 +19,8 @@ class DefaultTextStyle extends Inherited {
 
   final TextStyle style;
 
-  static TextStyle of(Component component) {
-    DefaultTextStyle result = component.inheritedOfType(DefaultTextStyle);
+  static TextStyle of(Widget widget) {
+    DefaultTextStyle result = widget.inheritedOfType(DefaultTextStyle);
     return result == null ? null : result.style;
   }
 

packages/flutter/lib/widgets/framework.dart

@@ -272,6 +272,27 @@ abstract class Widget {
     return ancestor;
   }
 
+  Set<Type> _dependencies;
+  Inherited inheritedOfType(Type targetType) {
+    if (_dependencies == null)
+      _dependencies = new Set<Type>();
+    _dependencies.add(targetType);
+    Widget ancestor = parent;
+    while (ancestor != null && ancestor.runtimeType != targetType)
+      ancestor = ancestor.parent;
+    return ancestor;
+  }
+
+  void dependenciesChanged() {
+    // This is called if you've use inheritedOfType and the Inherited
+    // ancestor you were provided was changed. For a widget to use Inherited
+    // it needs an implementation of dependenciesChanged. If your widget extends
+    // Component or RenderObjectWrapper this is provided for you automatically.
+    // If you aren't able to extend one of those classes, you need to
+    // provide your own implementation of dependenciesChanged.
+    assert(false);
+  }
+
   void remove() {
     _renderObject = null;
     setParent(null);
@@ -453,10 +474,9 @@ abstract class Inherited extends TagNode {
   void notifyDescendants() {
     final Type ourRuntimeType = runtimeType;
     void notifyChildren(Widget child) {
-      if (child is Component &&
-          child._dependencies != null &&
+      if (child._dependencies != null &&
           child._dependencies.contains(ourRuntimeType))
-        child._dependenciesChanged();
+          child.dependenciesChanged();
       if (child.runtimeType != ourRuntimeType)
         child.walkChildren(notifyChildren);
     }
@@ -608,17 +628,7 @@ abstract class Component extends Widget {
     _built.detachRoot();
   }
 
-  Set<Type> _dependencies;
-  Inherited inheritedOfType(Type targetType) {
-    if (_dependencies == null)
-      _dependencies = new Set<Type>();
-    _dependencies.add(targetType);
-    Widget ancestor = parent;
-    while (ancestor != null && ancestor.runtimeType != targetType)
-      ancestor = ancestor.parent;
-    return ancestor;
-  }
-  void _dependenciesChanged() {
+  void dependenciesChanged() {
     // called by Inherited.sync()
     _scheduleBuild();
   }
@@ -937,6 +947,11 @@ abstract class RenderObjectWrapper extends Widget {
     }
   }
 
+  void dependenciesChanged() {
+    // called by Inherited.sync()
+    syncRenderObject(this);
+  }
+
   void remove() {
     assert(renderObject != null);
     _nodeMap.remove(renderObject);

packages/flutter/lib/widgets/switch.dart

@@ -30,47 +30,34 @@ const Duration _kCheckDuration = const Duration(milliseconds: 200);
 const Size _kSwitchSize = const Size(_kSwitchWidth + 2.0, _kSwitchHeight + 2.0);
 const double _kReactionRadius = _kSwitchWidth / 2.0;
 
-class Switch extends Component {
-  Switch({Key key, this.value, this.onChanged}) : super(key: key);
-
-  final bool value;
-  final ValueChanged onChanged;
-
-  Widget build() {
-    return new _SwitchWrapper(
-        value: value,
-        onChanged: onChanged,
-        thumbColor: Theme.of(this).accentColor);
-  }
-}
-
-// This wrapper class exists only because Switch needs to be a Component in
-// order to get an accent color from a Theme but Components do not know how to
-// host RenderObjects.
-class _SwitchWrapper extends LeafRenderObjectWrapper {
-  _SwitchWrapper({Key key, this.value, this.onChanged, this.thumbColor})
+class Switch extends LeafRenderObjectWrapper {
+  Switch({ Key key, this.value, this.onChanged })
       : super(key: key);
 
   final bool value;
   final ValueChanged onChanged;
-  final Color thumbColor;
 
   _RenderSwitch get renderObject => super.renderObject;
   _RenderSwitch createNode() => new _RenderSwitch(
-      value: value, thumbColor: thumbColor, onChanged: onChanged);
+    value: value,
+    thumbColor: null,
+    onChanged: onChanged
+  );
 
-  void syncRenderObject(_SwitchWrapper old) {
+  void syncRenderObject(Switch old) {
     super.syncRenderObject(old);
     renderObject.value = value;
     renderObject.onChanged = onChanged;
-    renderObject.thumbColor = thumbColor;
+    renderObject.thumbColor = Theme.of(this).accentColor;
   }
 }
 
 class _RenderSwitch extends RenderToggleable {
-  _RenderSwitch(
-      {bool value, Color thumbColor: _kThumbOffColor, ValueChanged onChanged})
-      : _thumbColor = thumbColor,
+  _RenderSwitch({
+    bool value,
+    Color thumbColor: _kThumbOffColor,
+    ValueChanged onChanged
+  }) : _thumbColor = thumbColor,
         super(value: value, onChanged: onChanged, size: _kSwitchSize) {}
 
   Color _thumbColor;

packages/flutter/lib/widgets/theme.dart

@@ -23,8 +23,8 @@ class Theme extends Inherited {
 
   static final ThemeData _kFallbackTheme = new ThemeData.fallback();
 
-  static ThemeData of(Component component) {
-    Theme theme = component.inheritedOfType(Theme);
+  static ThemeData of(Widget widget) {
+    Theme theme = widget.inheritedOfType(Theme);
     return theme == null ? _kFallbackTheme : theme.data;
   }