set variables outside angular scope

if you need to assign to variables outside angular/ionic control, we need to use $apply function.

$scope.$apply(function() {
                          $scope.myFiles = userfiles;
 $scope.myFilesLength = $scope.myFiles.length;
                          });

this scenario came when i am doing the assignment in an callback function.

var AppControllers = angular.module('starter.controllers');

AppControllers
.controller('DownloadsPageCtrl',function($scope,$state,LDPServices,$cordovaDevice){
    //alert("in before enter downloads");
         
window.requestFileSystem(LocalFileSystem.PERSISTENT,0,function(fileSystem){
var FileStoredLoc = fileSystem.root.toURL()+"/LP/";
var dirEntry = fileSystem.root.getDirectory("LP",{create:true},gotDir);//fileSystem.root;
  }
}

function gotDir(dirEntry){
            //alert("direntry"+dirEntry);
            var dirReader = dirEntry.createReader();
            //alert("dirreader"+dirReader.readEntries);
            dirReader.readEntries(success,fail);

            }

function success(entries){
                //alert("succ:"+entries.length);
            //var AppDir = FileStoredLoc;//fileSystem.root.toURL()+"/LP/";
            var userfiles=[];
            for( i=0;i<entries.length;i++)
            {

            userfiles.push(entries[i].name);
           
            }
            //alert(userfiles.length);
            try
            {
            //var myf=["a.1","b.2"];
            //alert("b4");
            $scope.$apply(function() {
                          $scope.myFiles = userfiles;
 $scope.myFilesLength = $scope.myFiles.length;
                          });
           
            //alert("after");
            }
            catch(excp)
            {
$ionicPopup.alert({      
template: "Unable to open File" ,
okType:'button-positive'
});
            }
            }
html:
<ul class="list">
            <li ng-repeat="File in myFiles" class="item" ng-click="openFile(File)" ng-if="File != '.DS_Store'">
                {{File}}
            </li>
<div align="center" ng-if="myFilesLength == 0" style="color:white">
NO FILES TO BE SHOWN
</div>

        </ul>