Edit in JSFiddle

var app = angular.module('app', ['wj']);
app.controller('appCtrl', function ($scope) {
  $scope.cv = new wijmo.collections.CollectionView([{ value: -1 }, { value: 1 }, { value: 2 }]);
  // 回避方法
  // $scope.cv.getError = getError;
  $scope.initialized = function (s, e) {
    $scope.cv.getError = getError;
  }
});

var getError = function (item, property) {
  return item[property] < 0 ? 'エラー' : null;
};

<div ng-app="app" ng-controller="appCtrl">
  <wj-flex-grid items-source="cv" initialized="initialized(s,e)"></wj-flex-grid>
</div>