Parse: Query.find does not find data inside loop (even after using promises)

Question

I am actually passing two lists(existingLeaderboard and newResultSetObj) and i am comparing and querying them according to some logic. In the last i want to send notification to each user according to logic. But somehow my code does not wait for the find query(console log never shows up in the logs).Here is the code -

function compareAndSendNotification(existingLeaderboard, newResultSetObj) {
        var _ = require('underscore');
        var leadboardarray=[];
        console.log("New leaderboard" + newResultSetObj);
        console.log("Existing leaderboard" + existingLeaderboard);
        leadboardarray = existingLeaderboard;


        if (typeof existingLeaderboard == "undefined" || typeof newResultSetObj == "undefined"
            || existingLeaderboard.length == 0 || newResultSetObj.length == 0) {
            console.log("existingLeaderboard or newResultSetObj is null");
            return true;
        }

        var getUserFromLookPromise = Parse.Promise.as();

            var fromUser = "";
            //Event out looks


            _.each(existingLeaderboard, function(test) {
                if (contains(newResultSetObj, test)) {
                    console.log("Look id still in top 3 i =" + test);
                    // get user from look
                    var lookId = test;
                    console.log('get look id called ' + lookId);

                    var look = Parse.Object.extend("Look");
                    var lookQuery = new Parse.Query(look);
                    lookQuery.equalTo("objectId", lookId);

                    console.log("before find query");

                    //getUserFromLookPromise=getUserFromLookPromise.then(function(){
                    //     return lookQuery.find();
                    lookQuery.find().then(function(){
// following console log never prints 
                        console.log("inside find query");
                        var lookqueryPromise = Parse.Promise.as();
                        lookqueryPromise = lookqueryPromise.then(function() {
                            return lookQuery.find();
                        });
                        //while(lookqueryPromise.find().length==0){
                        //    lookqueryPromise.resolve(lookQuery.find());
                        //}
                        return lookqueryPromise;

                    }).then(function (notificationUser) {
                        console.log("inside resolve user");
                        if ( typeof notificationUser == "undefined" || notificationUser.length == 0 ) {
                            getUserFromLookPromise.resolve(notificationUser);
                        }
                        fromUser = notificationUser[0].get['fromUser'];
                        return fromUser;
                    }).then(function (user) {
                        console.log("sending notification to user " + user);
                        sendNotification(user, "hello");
                    });


                }
            });

        return getUserFromLookPromise;

    }

I am new to parse. Please let me know what i am doing wrong.

danh · Accepted Answer · 2015-12-05 22:14:17Z

1

Lets start with a smaller problem: Get a "Look" object given its id:

function lookWithId(objectId) {
    var query = new Parse.Query("Look");
    query.include("fromUser");  // presumes "fromUser" is a pointer to Parse.User
    return query.get(objectId);
}

Now, lets use that function to solve a bigger problem: Get an array of "Look" objects given an array of ids:

var _ = require('underscore');

function looksWithIds(objectIds) {
    var promises = _.map(objectIds, function(objectId) {
        return lookWithId(objectId);
    });
    return Parse.Promise.when(promises);
}

Now a tougher one. Given an array of users, send each one a message. This can be done only if your app associates Installations with Users by setting up a "user" pointer on each installation.

function sendMessageToUser(user) {
    var query = new Parse.Query(Parse.Installation);
    query.equalTo('user', user);
    return Parse.Push.send(where: query, data: { alert: "Hello" });
}

And pluralize that one as we did before...

function sendMessagesToUsers(users) {
    var promises = _.map(users, function(user) {
        return sendMessageToUser(user);
    });
    return Parse.Promise.when(promises);
}

One more function that you write: Given two leaderboards, return an array of "Look" object ids that meet some app criteria...

function lookIdsFromLeaderBoards(leaderBoardA, leaderBoardB) {
  // written by @user2922400, based on the app
  // no promises needed here, just answer an array of Look object ids
}

Now, the function you were attempting is as easy as pie:

function sendMessagesToLeader(leaderBoardA, leaderBoardB) {
    var lookIds = lookIdsFromLeaderBoards(leaderBoardA, leaderBoardB);
    return looksWithIds(lookIds).then(function(lookObjects) {
        var users = _.map(lookObjects, function(lookObject) {
            return lookObject.get("fromUser");
        });
        return sendMessagesToUsers(users);
    })
}

answered Dec 5, 2015 at 22:14

danh

62.7k10 gold badges100 silver badges139 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

user2922400 Over a year ago

Thanks danh for taking your time to answer my question. really appreciate this. However i am still stuck . I am using the same functions as you mentioned but this code only send message to first user and then it returns. not sure where i am going wrong. Here is the method that i modified according to my app needs. function lookWithId(objectId) { var query = new Parse.Query("Look"); query.equalTo("objectId", objectId); query.select("fromUser");//since it is not a direct ptr return query.find(); }

danh Over a year ago

Do you mean that an array of >1 users is delivered to sendMessagesToUsers (you can check this with console.log), but only one device is getting a push? Or is only one user in the array?

user2922400 Over a year ago

So multiple lookids are coming in return looksWithIds(lookIds) function but _.map(lookObjects, function(lookObject) { return lookObject.get("fromUser"); }); returns only one user and hence sendmessage is called for one user only.

danh Over a year ago

_.map over lookObjects will always return an array of equal length to lookObjects.length. Please log lookObjects and users just before the line return sendMessagesToUsers(users);. They must be the same length.

user2922400 Over a year ago

Thank you danh. You are right. Really appreciate your help.

Collectives™ on Stack Overflow

Parse: Query.find does not find data inside loop (even after using promises)

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related