Share async data between controllers without making multiple requests

Question

I\'m trying to make a single $http request to get one of my JSON files and use the data across all my controllers.

I saw on egghead.io how to share data acr

Answer 1

I like to store my data in the service, and return a promise to the controllers, because usually you need to deal with any errors there.

app.factory('Data', function($http, $q) {
   var data = [],
       lastRequestFailed = true,
       promise;
   return {
      getApps: function() {
         if(!promise || lastRequestFailed) {
            // $http returns a promise, so we don't need to create one with $q
            promise = $http.get('apps.json')
            .then(function(res) {
                lastRequestFailed = false;
                data = res.data;
                return data;
            }, function(res) {
                return $q.reject(res);
            });
         }
         return promise;
      }
   }
});

.controller('appInstallerListCtrl', ['$scope','Data',
function($scope, Data) {
    Data.getApps()
    .then(function(data) {
        $scope.data = data;
    }, function(res) {
        if(res.status === 500) {
            // server error, alert user somehow
        } else { 
            // probably deal with these errors differently
        }
    });
}]);

Any callbacks that are registered after a promise has been resolved/rejected will be resolved/rejected immediately with the same result/failure_reason. Once resolved/rejected, a promise can't change (its state). So the first controller to call getApps() will create the promise. Any other controllers that call getApps() will immediately get the promise returned instead.