Pass value to nested parse.com query callback

Question

So, using parse.com, I'm doing some nested queries... basically, getting an object and then retrieving its relations and doing some operations.

            pageQuery.find({
            success: function (results) {
                var pages = [];

                for (var result = 0; result < results.length; result++) {
                    var resArrayLength = pages.push(results[result].toJSON());
                    var indexOfLastPush = resArrayLength - 1;
                    console.log("resArrayLength = " + resArrayLength);
                    pages[indexOfLastPush].scrapeRules = new Array();
                    console.log("index of last push set to " + indexOfLastPush);
                    var relation = results[result].relation("RulesForPage");
                    //get the related scrape rules
                    relation.query().find({                            
                        success: function (rules) {
                            console.log("Found  " + rules.length + " rules");
                            for (var i = 0; i < rules.length; i++) {
                                console.log("rule index = " + i);
                                console.log("Found rule " + rules[i].id);
                                pages[indexOfLastPush].AllRules = new Array();

                                pages[indexOfLastPush].scrapeRules.push(rules[i].id);
                                console.log("pushed rule " + rules[i].get("name") + " to page at index " + indexOfLastPush);
                            }
                        }

                    });
                }

The problem I am seeing is that I am trying to indexOfLastPush to track an array index I need, but that value has changed by the time the call back has happened.

How can I pass it to the "success" callback so I have the index I need?

UPDATE: Thanks to @cggaurav for the excellent tip. Why does it seem like the answer to every JavaScript problem is to wrap your code in an anonymous function?

cggaurav · Accepted Answer · 2013-01-08 21:16:56Z

2

You have to have what is called a closure or an anonymous function for every relation.query() you make. See "More on lexical scoping" | http://mark-story.com/posts/view/picking-up-javascript-closures-and-lexical-scoping

answered Jan 8, 2013 at 21:16

cggaurav

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2 Comments

seanicus Over a year ago

Thanks for the reply... having read the article, I'm having trouble imagining how to implement that solution. Could I trouble you for some (pseudo) code to point me in the general direction?

cggaurav Over a year ago

(function(index) { //Do your relation.query() with 'index' here })(indexOfLastPush);

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