Callback called after promise completion with q nodejs

Question

Callback called after promise completion with q nodejs

I am using the Q promise library for making database calls. But before promise inside first then() completes, the second then() promise is started. The code is as follows:

var promise = Q.nfcall(function(){});
promise.then(removeFromOldList(data))
    .then(addToNewList(data))
    .done();

function removeFromOldList(data) {
    console.log('removeFromOldList');

    // remove the card from old list
    DB.ListTable.findOne({ _id : data.oldId},
        function(err, snippet) {
            if(err) console.error("An error occurred");
            if (err) console.error(err);

            console.log('removed the card from old list');
        })

}

function addToNewList(data) {
    console.log('addToNewList');

    // add the card to the new list
    DB.ListTable.findOne({ _id: data.newId},
        function(err, snippet) {
            if(err) console.error("An error occurred");
            if (err) console.error(err);

            console.log('add the card to the new list');
        })

}

The console log gives me:

removeFromOldList

addToNewList

removed the card from old list add the

card to the new list

How can i make the callbacks be executed before the promise is returned.

node.js
callback
q

Answer 1

The problem is the DB.ListTable.findOne calls are asynchronous, so node will go through both functions before even hitting the DB callbacks.

Can you try something like this:

var query1 = DB.ListTable.findOne({ _id : data.oldId}, function(err, snippet) {
        ...
    }).exec();
var query2 = DB.ListTable.findOne({ _id: data.newId}, function(err, snippet) {
        ...
    }).exec();
var promise = Q.nfcall(function(){});
promise
    .then(query1)
    .then(query2)
    .done();