如何获取嵌套的ng-repeat的长度

<div ng-repeat="outerItem in outerArray" outer-repeat>
  <div ng-repeat="innerItem in outerItem.innerArray" inner-repeat>
    <!-- 内层ng-repeat的内容 -->
  </div>
</div>

angular.module('myApp', [])
  .controller('myController', function($scope) {
    $scope.outerArray = [
      { innerArray: [1, 2, 3] },
      { innerArray: [4, 5, 6] },
      { innerArray: [7, 8, 9] }
    ];

    $scope.getNestedRepeatLength = function(outerIndex, innerIndex) {
      var outerElement = angular.element('[outer-repeat]').eq(outerIndex);
      var innerElement = outerElement.find('[inner-repeat]').eq(innerIndex);
      var innerLength = innerElement.children().length;
      return innerLength;
    };
  });