Error: scope.filter is not a function

[casper123]

Hi,
I'm using filter bar for on of my ionic project, however when I search an item, i get this error

ionic.bundle.js:25642 TypeError: scope.filter is not a function
    at Scope.scope.filterItems (ionic.filter.bar.js:559)
    at filterItems (ionic.filter.bar.js:132)
    at ionic.bundle.js:31021
    at completeOutstandingRequest (ionic.bundle.js:18706)
    at ionic.bundle.js:18978

This is my filter bar instance

$ionicFilterBar.show({
      filter: '',
      items: $scope.productList,
      filterProperties: 'itemDetails.item_title',
      update: function (filteredItems, filterText) {
        console.log(filterText);
        $scope.productList = filteredItems;
        if (filterText) {
          console.log(filterText);
        }
      }
    });