How to handle results of nested promises

Question

I'm having trouble refactoring some code to use Promises, this to avoid nesting callbacks, the code i'm trying to refactor looks like this:

bot.api.users.list({}, function(err, teamData) {
if(err) {
  bot.botkit.log("Couldn't fetch team data from API", err);
  return;
}

var members = teamData.members;
var msgSender = _.find(members, function(member) { return member.id == message.user });

parsedUserIds(userIdsGroup).forEach(function(id) {
  var msgReceiver = _.find(members, function(member) { return member.id == id });

  bot.startPrivateConversation({ user: id }, function(err, conversation) {
    if(err) {
      bot.botkit.log("Couldn't initiate private conversation", err);
      return;
    }

    var message = format("Hey {to}, {from} just requested a Pull Request Review, here's the link: {githubLink}, please go and check it out!", 
                         { to: msgReceiver.name,
                           from: msgSender.name,
                           githubLink: githubRepoUrl });

      conversation.say(message);
  });
});

I'm using botkit with the slack api, and bluebird for Promises.

The part of the code where I have the most trouble is with the loop that iterates through each id and starts a private conversation with a user; what i've been trying looks like this:

  var usersList = Promise.promisify(bot.api.users.list);
  var privateConversation = Promise.promisify(bot.startPrivateConversation);

  usersList({}).then(function(data) {
    var members = data.members;
    var msgSender = findMember(members, message.user);

    return Promise.all(parsedUserIds(userIdsGroup).map(function(id) {
      var msgReceiver = findMember(members, id);

      return privateConversation({ user: id }).then(function(conversation) {
        var message = format("Hey {to}, {from} just requested a Pull Request Review, here's the link: {githubLink}, please go and check it out!", 
                             { to: msgReceiver.name,
                               from: msgSender.name,
                               githubLink: githubRepoUrl });
        conversation.say(message);
      });
    }));
  }).catch(function(err){
    bot.botkit.log(err);
  });

From what I understand, Promise.all allows me to get a result from an array of promises... however, I'm getting an error from this code: TypeError: this.task.bot.reply is not a function which isn't helping me at all.

How can I use promises to accomplish what I'm trying to do?

score 2 · Answer 1 · answered Jun 04 '16 at 07:48

Promise.all allows me to get a result from an array of promises

Promise.all returns a promise that gets fulfilled once all the promises you passed in it are fulfilled. So what you need to do is to call then on it

Promise.all(parsedUserIds(userIdsGroup).map(function(id) {/*return promise here*/}))
.then(function(results) { console.log(results); })

How to handle results of nested promises

1 Answers1