feat(ngModel): bind to getters/setters

Closes angular#768

Author: btford

src/ng/directive/input.js

@@ -1807,7 +1807,12 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
       ctrl.$modelValue         = ctrl.$valid ? modelValue : undefined;
       ctrl.$$invalidModelValue = ctrl.$valid ? undefined : modelValue;
 
-      ngModelSet($scope, ctrl.$modelValue);
+      var getter = ngModelGet($scope);
+      if (typeof getter === 'function') {
+        getter(ctrl.$modelValue);
+      } else {
+        ngModelSet($scope, ctrl.$modelValue);
+      }
       forEach(ctrl.$viewChangeListeners, function(listener) {
         try {
           listener();
@@ -1883,6 +1888,10 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
   $scope.$watch(function ngModelWatch() {
     var modelValue = ngModelGet($scope);
 
+    if (typeof modelValue === 'function') {
+      modelValue = modelValue();
+    }
+
     // if scope model value and ngModel value are out of sync
     if (ctrl.$modelValue !== modelValue &&
         (isUndefined(ctrl.$$invalidModelValue) || ctrl.$$invalidModelValue != modelValue)) {

test/ng/directive/inputSpec.js

@@ -654,6 +654,30 @@ describe('input', function() {
   });
 
 
+  it('should bind to a getter', function() {
+    compileInput('<input type="text" ng-model="name" name="alias" ng-change="change()" />');
+
+    scope.$apply(function() {
+      scope.name = function () { return 'misko'; };
+    });
+
+    expect(inputElm.val()).toBe('misko');
+  });
+
+
+  it('should bind to a setter', function() {
+    compileInput('<input type="text" ng-model="name" name="alias" ng-change="change()" />');
+
+    var name = '';
+    scope.name = function (newName) {
+      return typeof newName !== 'undefined' ? (name = newName) : name;
+    };
+    changeInputValueTo('adam');
+    expect(inputElm.val()).toBe('adam');
+    expect(name).toBe('adam');
+  });
+
+
   it('should not set readonly or disabled property on ie7', function() {
     this.addMatchers({
       toBeOff: function(attributeName) {