How to use bluebird to chain consecutive callback functions such that they both have on catch block

Question

I have two callback functions from mongoose that I would like to chain using bluebird's then

My first callback function uses then successfully.

User.findOne().distinct(('Friends.id'), {id: req.body.myId}, {Friends: {$elemMatch: { gender: req.body.gender}}})
.then(function(IDs){

var results = //////some computation

})
.catch(function(error)) {


 } 

I just can't get the syntax right to chain the second callback function so that it shares the first callback function's catch method. In this case, I cannot use Promise.all because the second callback function is dependent on the first callback function's results. Anyway the second callback function is the following:

  User.find({Friends: { $not: { $elemMatch: { id: req.body.myId }}}, id: {$in: results}}, function(err, users){



})

Answer 1

You can chain two promises like this.

User.findOne().distinct(('Friends.id'), {id: req.body.myId}, {Friends: {$elemMatch: { gender: req.body.gender}}})
    .then(function(IDs){

        var results = //////some computation

        // second promise
        return User.find({Friends: { $not: { $elemMatch: { id: req.body.myId }}}, id: {$in: results}})
    })
    .then(function(friends) {
        // do something with the result of the second query
    })
    .catch(function(error)) {

    }