CODEWITHSUNDEEP
javascriptangularjsangular-promise
J.Olufsen
J.Olufsen

Reputation: 13915

Cannot execute chained promises

I need to get feed using $http.jsonp after that I return deferred.resolve(feed) which should pass feed value to chained function EntryStateUrlService.getEntryStateUrl.

For some reason it says FeedService.parseFeed(feedSrc) evaluated as undefined therefore then() method cannot be invoked on undefined. How to fix it?

app.service('LoadData', ['FeedService', 'EntryStateUrlService', '$q', function(FeedService, EntryStateUrlService, $q) {
    var deferred = $q.defer();

    this.loadData = function(feedSrc) {

        FeedService.parseFeed(feedSrc).then(EntryStateUrlService.getEntryStateUrl).then(function(urls) {
            $rootScope.links = urls;
        });
    }
}]); //TypeError: undefined is not a function

app.service('FeedService', function($http, $q) {
    var deferred = $q.defer();

    this.parseFeed = function(url) {
        $http.jsonp('//ajax.googleapis.com/ajax/services/feed/load?v=1.0&callback=JSON_CALLBACK&q=' + encodeURIComponent(url))
            .success(function(res) {

                deferred.resolve(res.data.responseData.feed.entries); //TypeError: Cannot read property 'responseData' of undefined
            }).error(function() {
                deferred.reject();
            });
 return deferred.promise(); //TypeError: object is not a function
    }
});
app.service('EntryStateUrlService', ['$state', '$q', function($state, $q) {
    var deferred = $q.defer();
    this.getEntryStateUrl = function(feeds) {
            var idx = 0;
            feeds.forEach(function(e) {
                $http.jsonp(e.link).success(function(data) {
                    /*stuff*/
                    deferred.resolve('root.' + generatedStateName);
                });
            }); //forEach
        } //getEntryStateUrl
return deferred.promise();
}]); //EntryStateUrlService

UPDATE

After adding return deferred.promise(); both to EntryStateUrlService and FeedService I am getting TypeError: object is not a function for return deferred.promise(); in FeedService.

Upvotes: 0

Views: 273

Answers (3)

Karthik Easwaran
Karthik Easwaran

Reputation: 504

In the FeedService return the deferred.promise, Also in the EntryStateUrlService, invoking the multiple service in the forEach, hence if the promise needs to be resolved once all the service completed, use $q.all as like below.

app.service('LoadData', ['FeedService', 'EntryStateUrlService', '$q', function(FeedService, EntryStateUrlService, $q) {
    this.loadData = function(feedSrc) {

        FeedService.parseFeed(feedSrc).then(EntryStateUrlService.getEntryStateUrl).then(function(urls) {
            $rootScope.links = urls;
        }, function(failureException) {
            // failure error handler comes here.        
        });
    }
}]); //TypeError: undefined is not a function

app.service('FeedService', function($http, $q) {

    this.parseFeed = function(url) {
        var deferred = $q.defer();
        $http.jsonp('//ajax.googleapis.com/ajax/services/feed/load?v=1.0&callback=JSON_CALLBACK&q=' + encodeURIComponent(url))
            .success(function(res) {

                deferred.resolve(res.data.responseData.feed.entries); //TypeError: Cannot read property 'responseData' of undefined
            }).error(function() {
                deferred.reject();
            });
        return deferred.promise;
    }
});
app.service('EntryStateUrlService', ['$state', '$q', function($state, $q) {

    this.getEntryStateUrl = function(feeds) {

            var deferred = $q.defer();
            var idx = 0, promises = [];
            feeds.forEach(function(e) {
                $http.jsonp(e.link).success(function(data) {
                    /*stuff*/                    
                });
            }); //forEach

            // once all the jsonp service in the  for loop is finished, then resolve the promise
            $q.all(promises).then(function() {
                deferred.resolve('root.' + generatedStateName);
            }, deferred.reject);

            return deferred.promise;

        } //getEntryStateUrl
}]); //EntryStateUrlService

Upvotes: 1

dec
dec

Reputation: 604

I'am missing a promise in your code. I think you have to return a promise inside your FeedService: return deferred.promise(); instead of return deferred;

Upvotes: 0

Chris Charles
Chris Charles

Reputation: 4446

Shouldn't you parseFeed function be returning the deferred?

this.parseFeed = function(url) {
    $http.jsonp('//ajax.googleapis.com/ajax/services/feed/load?v=1.0&callback=JSON_CALLBACK&q=' + encodeURIComponent(url))
        .success(function(res) {

            deferred.resolve(res.data.responseData.feed.entries);
        }).error(function() {
            deferred.reject();
        });
    return deferred;
}

Upvotes: 0

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