Returning the result of a promise

Question

function main() {
  matchUserToChatRoom(senderID)
    .then(function(chatRoom) {
      //FIXME: I want to be able to use chatRoom from the below function
      console.log(chatRoom)
    })
}

function matchUserToChatRoom(userId) {
  return models.User.findOne({where: {messenger_id: userId}})
    .then(function(user) {
       models.ChatRoom
        .findOrCreate({where: {status: "open"}, defaults: {status: "open"}})
        .spread(function(chatRoom, created) {
          chatRoom.addUser(user).then(function(chatRoom) {
            //FIXME: I want to use this "chatRoom" inside the main function
          })
        })
     })
  })
}

How do I return the chatRoom object, which is a result of nested promises, to the main function?

Where do `findOrCreate` and `spread` come from? Is it a COTS or custom code? — sp00m, Aug 19 '16 at 09:54

score 4 · Accepted Answer · answered Aug 19 '16 at 09:57

Do not forget to return the promises in order to be chained.

function matchUserToChatRoom(userId) {
  return models.User.findOne({where: {messenger_id: userId}})
    .then(function(user) {
       return models.ChatRoom
        .findOrCreate({where: {status: "open"}, defaults: {status: "open"}})
        .spread(function(chatRoom, created) {
          return chatRoom.addUser(user);
        })
     })
  })
}

score -1 · Answer 2 · answered Aug 19 '16 at 09:56

This is for getting idea. You need to use reject too.

function matchUserToChatRoom(userId) {
return new Promise(function(resolve, reject){
  models.User.findOne({where: {messenger_id: userId}})
    .then(function(user) {
       models.ChatRoom
        .findOrCreate({where: {status: "open"}, defaults: {status: "open"}})
        .spread(function(chatRoom, created) {
          chatRoom.addUser(user).then(function(chatRoom) {
             resolve(chatRoom);
            //FIXME: I want to use this "chatRoom" inside the main function
          })
        })
     })
  })
}
});

No, you **don't** need to create your own promise. That's the "promise constructor anti-pattern". — , Aug 19 '16 at 10:11

Returning the result of a promise

2 Answers2