blog/ngmodel/bindExpression

bind-expression.js

.directive("bindExpression", function($parse) {
  var directive = {};
  directive.restrict = 'E';
  directive.require = 'ngModel';
  directive.link = function(scope, element, attrs, ngModel) {
    scope.$watch(attrs.expression, function (newValue) {
      ngModel.$setViewValue(newValue);
    });
    ngModel.$render = function() {
      $parse(attrs.expression).assign(ngModel.viewValue);
    }
  };
  return directive;
});