Resolving a promise array

Question

I am having trouble in resolving a promise that is returned by firebase. This is an ionic - angularjs - firebase project that I am building to learn. The issue is that my function returns a promise that contains an array of 3 users but I am unable to unwrap this promise.

My code:

function eventusers(id) {
    var userarr = [];
    var deferred = $q.defer();

    // *The code below makes 2 firebase calls and returns an array of users*

    eventref.orderByChild("Eventid").equalTo(eventid).on("value", function(snap) {
        var users = snap.val();
        angular.forEach(users, function(value,key) {
            var obj = value;
            for (var prop in obj) {
                if(obj[prop] == "True") {
                    userref.child(prop).on("value", function (snap) {
                        var id = snap.val().email;
                        userarr.push(id);
                        console.log(userarr); // I am able to see the list of users here
                    });
                };
            }
        });
        deferred.resolve(userarr);
    });
    return deferred.promise;
};

//The console.log shows a promise (pls see the attached pic)
console.log(eventusers(eventid));

// I tried to loop through the response using angular.forEach and also a for loop but it does 
//not execute that part of the code as I do not see the response of the console.log. If I 
//replace the for loop with just console.log(response), then I get an empty array.

eventusers(eventid).then(function (response) {
    for (var i = 0; i <response.length; i++) {
        console.log(response[i]);
    }
});

Phil · Accepted Answer · 2016-07-28 07:20:21Z

Your deferred promise is resolving before the inner asynchronous action

userref.child(prop).on('value', ...

completes.

You'll need to wrap that in another deferred object then return a promise resolving all of the inner promises.

function eventusers(id) {
    return $q(function(resolve) {
        eventRef.orderByChild('Eventid').equalTo(id).on('value', function(snap) {
            var promises = [];
            snap.val().forEach(function(user) {
                angular.forEach(user, function(userProp, prop) {
                    if (userProp === 'True') {
                        promises.push($q(function(resolve) {
                            userref.child(prop).on('value', function(snap) {
                                resolve(snap.val().email);
                            });
                        }));
                    }
                });
            });

            resolve($q.all(promises));
        });
    });
}

eventusers(eventid).then(function (response) {
    for (var i = 0; i < response.length; i++) {
        console.log(response[i]);
    }
});

Romesh · Accepted Answer · 2016-07-28 07:24:37Z

0

Modify your code to

eventusers(eventid).then(function (response) {
var myArray = response.value;
for (var i = 0; i <myArray.length; i++) {
console.log(myArray[i]);
};

Since your array object is inside of promise object

You can also refer to Plunker

edited Jul 28, 2016 at 7:24

answered Jul 28, 2016 at 6:45

Romesh

2,3023 gold badges25 silver badges48 bronze badges

2 Comments

Phil Over a year ago

OP only pushes emails into userarr which is the resolve value so I'm not sure why you would think they have a value property

AjRev Over a year ago

Hi Romesh, Thanks for your time. I checked your plunker. myData contains the property 'value' (which is an array of values - ID:1 etc)using which you are able to access it in the getPromiseObject function. My promise object, returns an array containing 3 emails in the pattern: [0: email1, 1: email2, 2: email3].

Collectives™ on Stack Overflow

Resolving a promise array

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related