Index: pkg/polymer_expressions/lib/polymer_expressions.dart |
diff --git a/pkg/polymer_expressions/lib/polymer_expressions.dart b/pkg/polymer_expressions/lib/polymer_expressions.dart |
index a6defbe807ade69b464c2be53d5d60931f93e7f4..332e3a1ae9c2b8e8fa63b20e455718b44926847e 100644 |
--- a/pkg/polymer_expressions/lib/polymer_expressions.dart |
+++ b/pkg/polymer_expressions/lib/polymer_expressions.dart |
@@ -97,7 +97,7 @@ class PolymerExpressions extends BindingDelegate { |
? model |
: _scopeFactory.modelScope(model: model, variables: globals); |
if (oneTime) { |
- return _Binding._oneTime(expr, scope, null); |
+ return _Binding._oneTime(expr, scope); |
} |
return new _Binding(expr, scope); |
}; |
@@ -250,6 +250,23 @@ class PolymerExpressions extends BindingDelegate { |
} |
} |
+ /// Parse the expression string and return an expression tree. |
+ static Expression getExpression(String exprString) => |
+ new Parser(exprString).parse(); |
+ |
+ /// Determines the value of evaluating [expr] on the given [model] and returns |
+ /// either its value or a binding for it. If [oneTime] is true, it direclty |
+ /// returns the value. Otherwise, when [oneTime] is false, it returns a |
+ /// [Bindable] that besides evaluating the expression, it will also react to |
+ /// observable changes from the model and update the value accordingly. |
+ static getBinding(Expression expr, model, {Map<String, Object> globals, |
+ oneTime: false}) { |
+ if (globals == null) globals = new Map.from(DEFAULT_GLOBALS); |
+ var scope = model is Scope ? model |
+ : new Scope(model: model, variables: globals); |
+ return oneTime ? _Binding._oneTime(expr, scope) |
+ : new _Binding(expr, scope); |
+ } |
} |
typedef Object _Converter(Object); |
@@ -264,10 +281,9 @@ class _Binding extends Bindable { |
ExpressionObserver _observer; |
var _value; |
- _Binding(this._expr, this._scope, [converter]) |
- : _converter = converter == null ? _identity : converter; |
+ _Binding(this._expr, this._scope, [this._converter]); |
- static Object _oneTime(Expression expr, Scope scope, _Converter converter) { |
+ static Object _oneTime(Expression expr, Scope scope, [_Converter converter]) { |
try { |
var value = eval(expr, scope); |
return (converter == null) ? value : converter(value); |
@@ -280,7 +296,7 @@ class _Binding extends Bindable { |
bool _convertAndCheck(newValue, {bool skipChanges: false}) { |
var oldValue = _value; |
- _value = _converter(newValue); |
+ _value = _converter == null ? newValue : _converter(newValue); |
if (!skipChanges && _callback != null && oldValue != _value) { |
_callback(_value); |
@@ -296,7 +312,7 @@ class _Binding extends Bindable { |
_check(skipChanges: true); |
return _value; |
} |
- return _oneTime(_expr, _scope, _converter); |
+ return _Binding._oneTime(_expr, _scope, _converter); |
} |
set value(v) { |