Returning to the previously loaded DOM elements in AngularJS: Maintaining state when navigating back

I've developed an angular application with two main views:

1) List view

2) Detail View

When a user clicks on a thumbnail in the list view, they are directed to the detail view. Here is the route setup:

app.config(['$routeProvider',
  function($routeProvider) {
    $routeProvider.
      when('/list', {
        templateUrl: 'partials/list.html',
        controller: 'ListCtrl',

      }).
      when('/list/:id', {
        templateUrl: 'partials/detail.html',
        controller: 'DetailCtrl',

      }).
      otherwise({
        redirectTo: '/list'
      });
  }]);

The issue arises with the 'loadmore' function in the 'listCtrl' controller which loads additional content:

myControllers.controller('ListCtrl', ['$scope', '$location', 'Troll', '$http',

function ($scope, $location, Troll, $http) {
    // Code for loading trolls

    $scope.loadmore = function () {
        // AJAX call to load more data
        // Preserving newly loaded data
    }

}]);

PROBLEM: An issue occurs when navigating back to the list view after using the loadmore function - the newly loaded divs disappear. How can I preserve them?

Answer №1

Whenever you change routes, the controller responsible for that route is initialized upon loading the route and destroyed when the route is changed. As a result, the data gets lost because the controller is reinitialized and the previous data does not persist.

There are two solutions to this issue:

  1. Implement a higher-level controller that is not destroyed, potentially residing on the body element, passing its scope to child controllers. However, this method does not truly modularize concerns but can be useful for other issues like Authentication or Profile management.

  2. A better approach would be pulling the data into a service, such as listService, which fetches and caches the data, ensuring it remains available even when the route is changed.


An alternative solution could involve:

If there's a higher-level controller handling data fetching or if the data is moved to a service (recommended), the data loaded by the loadMore function will stay intact. It should reside in a parent scope that persists through route changes.

HTML:

<body ng-controller="ApplicationController">
     <!-- Code Here -->
</body>

Controller:

myControllers.controller('ApplicationController', function($scope) {
     var data = [];

     $scope.loadmore = function () {
        // Use Angular here!!! $http not jQuery! 
        // A complete Angular app can be built without relying on jQuery
        // Angular's implementation of jQuery Lite will be used
        jQuery.ajax({
            url: 'trolls/trolls.php?troll_index=' + $('#main-content #item-list .sub-item').size(),
            type: 'GET',
            async: false,
            data: {},
            dataType: 'json',
            success: function (response) {


                if (response != null) {
                    $.each(response, function (index, item) {

                        data.push({
                            UID: response[index].UID,
                            id: response[index].id,
                            popular: response[index].popular,
                            imageUrl: response[index].imageUrl,
                            name: response[index].name,
                            tags: response[index].tags,
                            category: response[index].category
                        });

                    });
                }

                return data;

            }
            error: function () {
                console.log('Failed!');
            }
        });

    }
});

However, this approach may seem hacky using jQuery.

Another approach utilizing a service for fetching and caching:

Moving the functionality to a service seems more appropriate.

myServices.factory('listService', function($http, $q) {

   var//iable declaration 
      service = {},
      list = []
   ;
   /////////////////////   
   //Private functions//
   /////////////////////

   function loadMore(url) {
      var deferred = $q.defer();

      $http({ method: 'GET', url: url }) // Need to pass in the specific URL maybe from the DOM scoped function?
      .success(function(data) {
         deferred.resolve(data);
      })
      .error(function() {
        deferred.reject();
        //Do error things
      });   

     return deferred.promise; 
   }

   ////////////////////
   //Public Functions//
   ////////////////////

   service.loadMore = function(url) { 
      // Used for loading more data
      loadMore(url).then(function(data) {
        list.push(data);
        return list
      });
   }

   service.getList = function() {
      // Returns the currently loaded data
      return list;
   }

 return service;

});

In your controller:

myControllers.controller('ListCtrl', ['$scope', '$location', 'Troll', listService

function ($scope, $location, Troll, listService) {
    $scope.Trolls = Troll.query();
    $scope.orderProp = 'popular';
    $scope.fromData = {};


    $scope.loadmore = function(subItemSize) { //add url specific params here
       var url = 'trolls/trolls.php?troll_index=' + subItemSize;
       return listService.loadMore(url);
    };

}]);

Answer №2

Consider using ui-router for enhanced functionality: https://github.com/angular-ui/ui-router. With ui-router, you can utilize multiple ui-view elements and implement relative routes. By defining child states, the parent state remains unaffected when transitioning to a child state. For further information, watch this informative video tutorial:

To see an example in action, check out my plunker demo:http://plnkr.co/edit/FA3DuHgngKD2CIPG5bHW?p=preview

Answer №3

While you can save information in a service or cache it using Angular's cache mechanism, the content of your div elements will not persist when navigating back to that specific view.

To ensure that the state of the DOM is also retained, consider utilizing an extension for ui-router known as ui-router-extras. This tool features a demonstration showcasing seamless state transitions and complete preservation of the DOM while switching between tabs.

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