propagating callback function to mongoose functions

Question

    TopicStatistics.methods.createTopicStatistics = function(callback)
    {
        // do stuff

        Topic.find({} , function (err, resultList)
        {
             if(err)
             {
                 // do stuff
                 if(typeof callback === "function")
                    callback(err); // callback undefined
             }
             else
             {
                 // do stuff
                 if(typeof callback === "function")
                    callback(null); // callback undefined
             }

        });
    };

Above is the code which I am trying to execute. The problem is this:

Since mongoose topic is asynchronous my function finalizes before the mongoose.find does its work which is normal and also because of this the callback variable is cleaned and it becomes undefined.

What I am looking for is a way to propagate the callback function to the mongoose.find function. Something like this:

Topic.find({} , function (err, resultList, mycallback);

that will enable me to use it inside my mongoose blob and to be able to call it when operations inside mongoose blob has ended.

Your first attempt should work IMO (without passing mycallback to Topic.find's function). If the callback is undefined it must be undefined. I.e. you're not passing anything to TopicStatistics.createTopicStatistics — laggingreflex
– laggingreflex, Commented Nov 1, 2014 at 4:51
you were right it was the function which I was passing incorrectly. — ralzaul
– ralzaul, Commented Nov 3, 2014 at 14:44

MVH · Accepted Answer · 2014-11-01 01:04:21Z

3

I think you need another callback defined in the scope of Topic.

Topic.find({} , function (err, resultList, callback)
    {

The "callback" variable you're using inside Topic.find() references back to the one set on TopicStatistics.createTopicStatistics(). So when you enter

Topic.find({} , function (err, resultList, mycallback);

the "mycallback" disappears since JavaScript doesn't check parameter count.

answered Nov 1, 2014 at 1:04

MVH

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3 Comments

ralzaul Over a year ago

I could not understand exactly what you have meant. Could you please give an example of the correct implementation?

MVH Over a year ago

I agree with laggingreflex above. I misread and thought you were defining Topic.find() in your example, but I see now that you were USING Topic.find() inside createTopicStatistics().

MVH Over a year ago

Some other things you might look at are the timings between when you create and save your mongoose models. To give a better answer, I would need to see more of your code to understand these timings. You might try referencing 'Topic' as this.model('Topic'). See the Mongoose docs (mongoosejs.com/docs/guide.html). There's an example under the heading 'Instance methods'.

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