Is this a “Deferred Antipattern”?

Question

I\'m finding it hard to understand the \"deferred antipattern\". I think I understand it in principal but I haven\'t seen a super simple example of what a service, with a di

Answer 1

Is this a “Deferred Antipattern”?

Yes, it is. 'Deferred anti-pattern' happens when a new redundant deferred object is created to be resolved from inside a promise chain. In your case you are using $q to return a promise for something that implicitly returns a promise. You already have a Promise object($http service itself returns a promise), so you just need to return it!

Here's the super simple example of what a service, with a deferred promise and one with antipattern look like,

This is anti-pattern

app.factory("SomeFactory",['$http','$q']){
    return {
        getData: function(){
            var deferred = $q.defer();            
            $http.get(destinationFactory.url)
              .then(function (response) {        
                 deferred.resolve(response.data);
            })
              .catch(function (error) {
                deferred.reject(error);
            });            
            return deferred.promise;
        }
     }
}])

This is what you should do

app.factory("SomeFactory",['$http']){
    return {
        getData: function(){
           //$http itself returns a promise 
            return $http.get(destinationFactory.url);
        }
}

while both of them are consumed in the same way.

this.var = SomeFactory.getData()
    .then(function(response) {
        //some variable = response;
    },function(response) {
        //Do error handling here
});

There's nothing wrong with either examples(atleast syntactically)..but first one is redundant..and not needed!

Hope it helps :)