fix(ng-pluralize): use ${..} to interpolate

See: #528 (comment)

Closes #572

Author: technohippy

lib/core/interpolate.dart

@@ -1,10 +1,5 @@
 part of angular.core;
 
-String _startSymbol = '{{';
-String _endSymbol = '}}';
-int _startSymbolLength = _startSymbol.length;
-int _endSymbolLength = _endSymbol.length;
-
 class Interpolation {
   final String template;
   final List<String> seperators;
@@ -48,8 +43,13 @@ class Interpolate {
    *      have embedded expression in order to return an interpolation function.
    *      Strings with no embedded expression will return null for the
    *      interpolation function.
+   * - `startSymbol`: The symbol to start interpolation. '{{' by default.
+   * - `endSymbol`: The symbol to end interpolation. '}}' by default.
    */
-  Interpolation call(String template, [bool mustHaveExpression = false]) {
+  Interpolation call(String template, [bool mustHaveExpression = false, 
+      String startSymbol = '{{', String endSymbol = '}}']) {
+    int startSymbolLength = startSymbol.length;
+    int endSymbolLength = endSymbol.length;
     int startIndex;
     int endIndex;
     int index = 0;
@@ -61,13 +61,13 @@ class Interpolate {
     List<Getter> watchExpressions = [];
 
     while(index < length) {
-      if ( ((startIndex = template.indexOf(_startSymbol, index)) != -1) &&
-           ((endIndex = template.indexOf(_endSymbol, startIndex + _startSymbolLength)) != -1) ) {
+      if ( ((startIndex = template.indexOf(startSymbol, index)) != -1) &&
+           ((endIndex = template.indexOf(endSymbol, startIndex + startSymbolLength)) != -1) ) {
         separators.add(template.substring(index, startIndex));
-        exp = template.substring(startIndex + _startSymbolLength, endIndex);
+        exp = template.substring(startIndex + startSymbolLength, endIndex);
         Expression expression = _parse(exp);
         watchExpressions.add(expression.eval);
-        index = endIndex + _endSymbolLength;
+        index = endIndex + endSymbolLength;
         hasInterpolation = true;
       } else {
         // we did not find anything, so we have to add the remainder to the chunks array

lib/directive/ng_pluralize.dart

@@ -63,10 +63,10 @@ part of angular.directive;
  *
  *    <ng-pluralize count="personCount" offset=2
  *                  when="{'0': 'Nobody is viewing.',
- *                         '1': '{{person1}} is viewing.',
- *                         '2': '{{person1}} and {{person2}} are viewing.',
- *                         'one': '{{person1}}, {{person2}} and one other person are viewing.',
- *                         'other': '{{person1}}, {{person2}} and {} other people are viewing.'}">
+ *                         '1': '${person1} is viewing.',
+ *                         '2': '${person1} and ${person2} are viewing.',
+ *                         'one': '${person1}, ${person2} and one other person are viewing.',
+ *                         'other': '${person1}, ${person2} and {} other people are viewing.'}">
  *    </ng-pluralize>
  *
  * Notice that we are still using two plural categories(one, other), but we added
@@ -153,7 +153,7 @@ class NgPluralizeDirective {
   }
 
   _setAndWatch(expression) {
-    var interpolation = interpolate(expression);
+    var interpolation = interpolate(expression, false, '\${', '}');
     interpolation.setter = (text) => element.text = text;
     interpolation.setter(expression);
     scope.$watchSet(interpolation.watchExpressions, interpolation.call);

test/directive/ng_pluralize_spec.dart

@@ -147,18 +147,18 @@ main() {
         var element = _.compile(
             "<ng-pluralize count='viewCount'  offset='2' " +
                 "when=\"{'0': 'Nobody is viewing.'," +
-                "'1': '{{p1}} is viewing.'," +
-                "'2': '{{p1}} and {{p2}} are viewing.'," +
-                "'one': '{{p1}}, {{p2}} and one other person are viewing.'," +
-                "'other': '{{p1}}, {{p2}} and {} other people are viewing.'}\">" +
+                "'1': '\${p1} is viewing.'," +
+                "'2': '\${p1} and \${p2} are viewing.'," +
+                "'one': '\${p1}, \${p2} and one other person are viewing.'," +
+                "'other': '\${p1}, \${p2} and {} other people are viewing.'}\">" +
             "</ng-pluralize>");
         var elementAlt = _.compile(
             "<ng-pluralize count='viewCount'  offset='2' " +
                 "when-0='Nobody is viewing.'" +
-                "when-1='{{p1}} is viewing.'" +
-                "when-2='{{p1}} and {{p2}} are viewing.'" +
-                "when-one='{{p1}}, {{p2}} and one other person are viewing.'" +
-                "when-other='{{p1}}, {{p2}} and {} other people are viewing.'>" +
+                "when-1='\${p1} is viewing.'" +
+                "when-2='\${p1} and \${p2} are viewing.'" +
+                "when-one='\${p1}, \${p2} and one other person are viewing.'" +
+                "when-other='\${p1}, \${p2} and {} other people are viewing.'>" +
             "</ng-pluralize>");
         _.rootScope.p1 = 'Igor';
         _.rootScope.p2 = 'Misko';