port TemplateBinding to ed3266266e751b5ab1f75f8e0509d0d5f0ef35d8

pkg/polymer_expressions/lib/polymer_expressions.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * A binding delegate used with Polymer elements that
  * allows for complex binding expressions, including
  * property access, function invocation,
  * list/map indexing, and two-way filtering.
  *
@@ skipping 49 matching lines @@
 
   /**
    * Creates a new binding delegate for Polymer expressions, with the provided
    * variables used as [globals]. If no globals are supplied, a copy of the
    * [DEFAULT_GLOBALS] will be used.
    */
   PolymerExpressions({Map<String, Object> globals})
       : globals = (globals == null) ?
           new Map<String, Object>.from(DEFAULT_GLOBALS) : globals;
 
-  _Binding getBinding(model, String path, name, node) {
+  prepareBinding(String path, name, node) {
     if (path == null) return null;
     var expr = new Parser(path).parse();
-    if (model is! Scope) {
-      model = new Scope(model: model, variables: globals);
-    }
-    if (node is Element && name == "class") {
-      return new _Binding(expr, model, _classAttributeConverter);
-    }
-    if (node is Element && name == "style") {
-      return new _Binding(expr, model, _styleAttributeConverter);
-    }
-    return new _Binding(expr, model);
+    return (model, node) {
+      if (model is! Scope) {
+        model = new Scope(model: model, variables: globals);
+      }
+      if (node is Element && name == "class") {
+        return new _Binding(expr, model, _classAttributeConverter);
+      }
+      if (node is Element && name == "style") {
+        return new _Binding(expr, model, _styleAttributeConverter);
+      }
+      return new _Binding(expr, model);
+    };
   }
 
-  getInstanceModel(Element template, model) {
+  prepareInstanceModel(Element template) => (model) {
     if (model is! Scope) {
-      var _scope = new Scope(model: model, variables: globals);
-      return _scope;
+      return new Scope(model: model, variables: globals);

[Siggi Cherem (dart-lang), 2013/10/29 21:00:07]

now it might fit with the prev line or even a ternary expr?

 prepareInstanceModel(Element template) =>
     (model) => model is Scope ? model : new Scope(model:model, variables:
globals);

[Jennifer Messerly, 2013/10/29 23:07:19]

haha. nice. done!

     }
     return model;
-  }
+  };
 }
 
 class _Binding extends ChangeNotifier {
   final Scope _scope;
   final ExpressionObserver _expr;
   final _converter;
   var _value;
 
   _Binding(Expression expr, Scope scope, [this._converter])
       : _expr = observe(expr, scope),
@@ skipping 29 matching lines @@
   @reflectable get value => _value;
 
   @reflectable set value(v) {
     try {
       assign(_expr, v, _scope);
     } on EvalException catch (e) {
       _logger.warning("Error evaluating expression '$_expr': ${e.message}");
     }
   }
 }