Simple support for routing in Sky

sky/sdk/lib/widgets/navigator.dart

Index: sky/sdk/lib/widgets/navigator.dart
diff --git a/sky/sdk/lib/widgets/navigator.dart b/sky/sdk/lib/widgets/navigator.dart
new file mode 100644
index 0000000000000000000000000000000000000000..dc4c0bc9ab28fd4d5007f81e7c3bae2cfeeafd76
--- /dev/null
+++ b/sky/sdk/lib/widgets/navigator.dart
@@ -0,0 +1,57 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'basic.dart';
+
+typedef UINode Builder(Navigator navigator);
+
+abstract class RouteBase {
+  RouteBase({this.name});

[Hixie, 2015/06/16 16:55:09]

Spaces around the parameters.

[jackson, 2015/06/16 18:27:27]

Done.

+  final String name;
+  UINode build(Navigator navigator);
+}
+
+class Route extends RouteBase {
+  Route({String name, this.builder}) : super(name: name);

[Hixie, 2015/06/16 16:55:09]

Spaces here too.

[jackson, 2015/06/16 18:27:27]

Done.

+  final Builder builder;
+  UINode build(Navigator navigator) => builder(navigator);
+}
+
+class Navigator extends Component {
+  Navigator({Object key, this.currentRoute, this.routes})

[Hixie, 2015/06/16 16:55:09]

Here too.

[jackson, 2015/06/16 18:27:27]

Done.

+    : super(key: key, stateful: true);
+
+  RouteBase currentRoute;
+  List<RouteBase> routes;

[Hixie, 2015/06/16 16:55:09]

Maybe add a comment that "routes" is just the _named_ routes.

Also, why is this a list, and not a map? The only use for it is looking things
up by key, no?

[jackson, 2015/06/16 18:27:27]

I'll rename it to namedRoutes for now and make it a map with a default key. I
think we're going to come up with a more advanced routing system, and a map data
structure might not work well for that, but right now it's fine.

+ 
+  void syncFields(Navigator source) {
+    currentRoute = source.currentRoute;
+    routes = source.routes;
+  }
+
+  void pushNamedRoute(String name) {

[Hixie, 2015/06/16 16:55:09]

Why "push"?

[jackson, 2015/06/16 18:27:27]

Because I'm implementing pop shortly. :)

+    assert(routes != null);
+    for (RouteBase route in routes) {

[Hixie, 2015/06/16 16:55:09]

You can do this way more efficiently if you use a map.

[jackson, 2015/06/16 18:27:27]

Agree, but see above

+      if (route.name == name) {
+        setState(() {
+          currentRoute = route;
+        });
+        return;
+      }
+    }
+    assert(false);  // route not found
+  }
+
+  void pushRoute(RouteBase route) {
+    setState(() {
+      currentRoute = route;
+    });
+  }
+
+  UINode build() {
+    Route route = currentRoute == null ? routes[0] : currentRoute;

[Hixie, 2015/06/16 16:55:09]

If you switch to using a map, then maybe have an implicitly default key rather
than taking the first in the list.

[jackson, 2015/06/16 18:27:27]

OK

+    assert(route != null);
+    return route.build(this);
+  }
+}