$q promise with Underscore _each

Question

So I have a method in a angularjs server that is calling a method that returns a promise for each method in a array. I am using underscore _each to loop through the array. I

Answer 1

after I read the question and the according answer, I got on the right track. Thanks so far! But for the final working soltion I spent another hour to get all use cases working. That's why I would like to share a code example which contains chained promises including an array of promises to wait for resolution.

Use case background is a server-side (nodeJs) file import after upload. I used promises in order to return an appropriate http status and result.

readFile: function (fileName) {
    if (fileName) {
        var deferred = Q.defer();
        var self = this;
        converter({input: fileName}, function (error, userData) {
            if (error) {
                deferred.reject(error);
            }
            self.storeUsers(error, userData)
                .then(function (success) {
                    if (success) {
                        deferred.resolve(success)
                    }
                })
                .fail(function (error) {                       
                    deferred.reject(error)                      
                });
        });
        return deferred.promise;
    }
},

storeUsers: function (error, data) {
    return Q.all(_.map(data, function (users, emailAddress) {
        var deferred = Q.defer();
        userRepository.findUserByEmail(emailAddress, function (user) {
            //...
            user.save(function (error) {
                if (error) {
                    deferred.reject(error);
                } else {
                    deferred.resolve(emailAddress);
                }
            });

        });
        return deferred.promise;
    }));
}

Hope that helps too!

Cheers Ben