Query Inside Parse Cloud For Loop

Question

I have been trying to run my Parse Cloud Code for some time and can not seem to get around this problem:

I have an array of Parse objectId's called IDArray. I then am sending the array as a parameter of a PFCloud call. Once the array has been sent to the Cloud Code, I can not seem to successfully create a for loop that goes through and updates a number value stored as "points" on Parse for each objectId.

In a nutshell, this is all I am trying to accomplish:

I just need to be able to have the for loop go through each objectId and perform an action for each ID.

I have been trying to get this to work for some time but have had no luck. Here is the code that I have been trying to manipulate - hopefully it will give someone a starting point to answer my question.

Parse.Cloud.define('updateAllUsers', function(request, response) {
    var UserData = Parse.Object.extend('UserData');
    var query = new Parse.Query(UserData);
    var list = request.params.listID;
    var currentuser = request.params.user;

                   
    for (var i = 0; i < list.length; i++) {
                   
        var userdata = list[i];        
        query.get(userdata, {
                                       
            success: function(UserData) {
                               
                response.success('Should add up');
                UserData.addUnique('Done', +1);
                UserData.save();
            },
            error: function() {
                response.error('something went wrong' );
            }
        });
    }
});

If someone could please help me with this I would be very grateful. Thank you

What is the value of request.params.listID at runtime? And do you go down the error path? — Kevin Boucher
– Kevin Boucher, Commented Aug 13, 2015 at 23:49
the value of "listID" is an array that contains Parse objectId's. And this is the error that I am receiving in my NSLog: [Error]: Error: Can't call success/error multiple times — Will Ullrich
– Will Ullrich, Commented Aug 14, 2015 at 0:00
@KevinBoucher not really sure where to go from here. I have been trying to get this to work using promises, but I cant seem to get it right — Will Ullrich
– Will Ullrich, Commented Aug 14, 2015 at 0:22
I think it's because you are using the same Parse.Query over and over again. Move the query assignment into the loop. — Kevin Boucher
– Kevin Boucher, Commented Aug 14, 2015 at 1:21

mido · Accepted Answer · 2015-08-14 01:59:34Z

1

I think the problem is you are sending response multiple times, you should wait for all the promises to finish and then send a response:

Parse.Cloud.define('updateAllUsers', function(request, response) {
    var UserData = Parse.Object.extend('UserData');
    var query = new Parse.Query(UserData);
    var list = request.params.listID;
    var currentuser = request.params.user;

    function checkUserData(userdata){   // returns parse promise for a particular userdata
        return query.get(userdata).then(function(){
            UserData.addUnique('Done', +1);
            UserData.save();            
        });
    }

    Parse.Promise.when(list.map(checkUserData)) // mapping all the elements in the list to resp promises
        .then(function(){   // on success
            response.success('Should add up');
        }).catch(function(e){    // on failure
             response.error('something went wrong' );
        });
});

Edit: if for some reason map is not available( in case of older browsers or list not being an normal javascript array), you can do something like:

Parse.Cloud.define('updateAllUsers', function(request, response) {
    var UserData = Parse.Object.extend('UserData');
    var query = new Parse.Query(UserData);
    var list = request.params.listID;
    var currentuser = request.params.user;
    var promises = [];
    function checkUserData(userdata){   // returns parse promise for a particular userdata
        return query.get(userdata).then(function(){
            UserData.addUnique('Done', +1);
            UserData.save();            
        });
    }

    for(var i=0;i<list.length;i++){
        promises.push(checkUserData(list[i]));
    }


    Parse.Promise.when(promises) // once all the promises are resolved...
        .then(function(){   // on success
            response.success('Should add up');
        }).catch(function(e){    // on failure
             response.error('something went wrong' );
        });
});

edited Aug 14, 2015 at 1:59

answered Aug 14, 2015 at 1:22

mido

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9 Comments

Will Ullrich Over a year ago

thanks for your help so far. I am new to this so bare with me lol. So this will take the "n" items (which are all objectId's from "listID") and create promises for those n items? Im confused on how this will loop through each of the items separately. However I did try using this but received this: [Error]: function not found (Code: 141, Version: 1.7.5)

Will Ullrich Over a year ago

yes i created list as an NSArray. currently it has 4 test objectId values but it will need to be some number later on when this works

Will Ullrich Over a year ago

I am pulling the list array from my xcode project - not sure if that is clear or if it changes things

mido Over a year ago

@WillVonUllrich you can try my second option then, one without map, also spraying console.log all over the place might give a clearer idea where the error is coming from

Will Ullrich Over a year ago

alright. last question: the checkUserData function - does that work in conjunction with the Parse.Promise... after the for loop?

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