How to create callback post saving an array of objects?

Question

Assuming I have the following in a function:

exports.addnames = function(req, res) {
    var names = ["Kelley", "Amy", "Mark"];

    for(var i = 0; i < names.length; i++) {
        (function (name_now) {
            Person.findOne({ name: name_now},
                function(err, doc) {
                    if(!err && !doc) {
                        var personDoc = new PersonDoc();
                        personDoc.name = name_now;
                        console.log(personDoc.name);
                        personDoc.save(function(err) {});
                    } else if(!err) {
                        console.log("Person is in the system");
                    } else {
                        console.log("ERROR: " + err);
                    }
                }
            );   
        )(names[i]);
    }

My issue is after I save the names, I want to return the results:

Person.find({}, function(err, doc) {    
    res.json(200, doc);
})

Though I have a callback for names, it appears that the last block of code (Persons.find({})) gets executed before the calls to save all the names is complete... thusly when the user goes to the url in the browser, "doc" is empty... Is there some way I can ensure that the Persons.find({}) is called after the for loop completes?

Bill · Accepted Answer · 2012-09-25 22:28:26Z

1

The easiest way to do things like this is to use an async library like the aptly named async which can be found at https://github.com/caolan/async.

If you have a list of names that you want to save and then return when complete, it would look like:

// save each of the names asynchronously
async.forEach(names, function(name, done) {
    Person.findOne({name: name},
        function(err, doc) {
            // return immediately if there was an error
            if(err) return done(err);

            // save the person if it doesn't already exist
            if(!doc) {
                var personDoc = new PersonDoc();
                personDoc.name = name;
                console.log(personDoc.name);

                // the async call is complete after the save completes
                return personDoc.save(done);
            } 

            // or if the name is already there, just return successfully
            console.log("Person is in the system");
            done();
        }
    );           
},
// this function is called after all of the names have been saved
// or as soon as an error occurs
function(err) {
    if(err) return console.log('ERROR: ' + err);

    Person.find({}, function(err, doc) {    
        res.json(200, doc);
    })

});

edited Sep 25, 2012 at 22:28

answered Sep 25, 2012 at 22:17

Bill

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1 Comment

Bill Over a year ago

That means that done is not being called for some reason (I think 1 minute is the async timeOut). You'll need to narrow down what the problem is - you can start with commenting out Person.findOne entirely and just call done(); immediately. The final function should be called immediately.

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