Using Promise With Parse Javascript Code to avoid asynchronous task

Question

I'm very new with Parse javascript code and i have a problem with asynchronous tasks. So i think that i have to use Promise.

So the goal of my code is to get users that created a sport event and to send them a notification after i get them. Because of asynchronous tasks, the code to send the notifications is reached before getting the users id with a Parse query.find method.

Here is my code:

//Background job whos goal is to send a push to the creator and the participants of 
// a sport event

Parse.Cloud.job("sendPushOneHourBefore", function(request, response) {
var query = new Parse.Query("SportEvent");
var now = new Date();
now.setHours(now.getHours()+1);

query.greaterThan("date", now);
now.setMinutes(now.getMinutes()+30);
query.lessThan("date", now);
query.include("_User");
var userIds = [];

//Request to find all the sport events within an hour and a half
return query.find().then(function(sportevents) {


      //getting the ids of the sportevent user's
      for (var i = 0; i < sportevents.length; ++i) {
            var userRelation = sportevents[i].relation("user"); 
            userRelation.query().find().then(function(users){
                { for (var j in users) 
                    { 
                        console.log(users[j].id);
                        userIds[i] = users[j].id;
                        console.log("userIds[i]"+userIds[i]);
                        console.log("i:"+i);
                        console.log("userIds[0]"+userIds[0]);
                        console.log("userIds[1]"+userIds[1]);
                    }     
                }
          }
                );

//          );

      }     

      return Parse.Promise.as("Hello");

    }.then(function(hello){
      console.error("Error finding sport events " + error.code + ": " + error.message);
      console.log("userIds[1] dans find-"+userIds[1]+"-");
      var queryPush = new Parse.Query(Parse.Installation);
      queryPush.containedIn('userId', userIds);

      Parse.Push.send({
              where: queryPush,
              data: {
                alert: "Votre evenement sportif va commencer bientot! Verifiez l'heure sur Whatteam!"
              }
            }, {
              success: function() {
                // Push was successful
              },
              error: function(error) {
                // Handle error
              }
        });

      return Parse.Promise.as("Hello");
    }),function(error) {

  }
);



});

When i run this job, i have this message:

return Parse.Promise.as("Hello");

    } has no method 'then'
    at main.js:99:6

Thanks a lot to anyone who can help me.

Sebastien

Thanks a lot for your answer eth3lbert! You were wright. i also had to remove console.error to run it. But i don't understand why "then(function(hello)" is not called after "userRelation.query().find().then(function(users)". do you have an idea about that problem please? — Sebastien Cavaignac
– Sebastien Cavaignac, Commented Nov 27, 2014 at 22:30

eth3lbert · Accepted Answer · 2014-11-27 23:29:11Z

1

To chain the promises in series, you could write as following:

...
//Request to find all the sport events within an hour and a half
return query.find().then(function(sportevents) {
    var promise = Parse.Proimse.as();
    //getting the ids of the sportevent user's
    for (var i = 0; i < sportevents.length; ++i) {
        var relationQuery = sportevents[i].relation("user").query(); 
        promise = promise.then(function(){
            return relationQuery.find().then(function(users) {
                for (var j in users) { 
                        console.log(users[j].id);
                        userIds[i] = users[j].id;
                        console.log("userIds[i]"+userIds[i]);
                        console.log("i:"+i);
                        console.log("userIds[0]"+userIds[0]);
                        console.log("userIds[1]"+userIds[1]);
                }
                return Parse.Promise.as('Hello')
            });
        });

    }
    return promise

}).then(...)

And also take a look at Promise in Series section in docs.

answered Nov 27, 2014 at 23:29

eth3lbert

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1 Comment

Sebastien Cavaignac Over a year ago

Thanks again. Your answer is great! I just corrected the "Parse.Proimse.as();" to "Parse.Promise.as();" and removed r"eturn Parse.Promise.as('Hello')" and also added ";" at the end of "return promise".

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