Bluebird Promisfy.each, with for-loops and if-statements?

问题

Right now, the parent for-loop (m < repliesIDsArray.length) completes before the first findOne fires, so this all only loops through the last element of the repliesIDsArray..asynchronous..

What's the proper syntax for a promisified version of this codeset? Am new to promisification, and wondering how to start this promisify + loop through arrays + account for if-statements..

Bluebird is required, and Promise.promisifyAll(require("mongoose")); is called.

for(var m=0; m<repliesIDsArray.length; m++){

objectID = repliesIDsArray[m];

Models.Message.findOne({ "_id": req.params.message_id},
    function (err, doc) {
        if (doc) {
         // loop over doc.replies to find the index(index1) of objectID at replies[index]._id
         var index1;
         for(var i=0; i<doc.replies.length; i++){
            if (doc.replies[i]._id == objectID) {
                index1 = i;
                break;
            }
         }
         // loop over doc.replies[index1].to and find the index(index2) of res.locals.username at replies[index1].to[index2]
         var index2;
         for(var j=0; j<doc.replies[index1].to.length; j++){
            if (doc.replies[index1].to[j].username === res.locals.username) {
                index2 = j;
                break;
            }
         }

         doc.replies[index1].to[index2].read.marked = true;
         doc.replies[index1].to[index2].read.datetime = req.body.datetimeRead;
         doc.replies[index1].to[index2].updated= req.body.datetimeRead;
         doc.markModified('replies');
         doc.save();
    }
}); // .save() read.marked:true for each replyID of this Message for res.locals.username

} // for loop of repliesIDsArray

回答1:

As Benjamin said, instead of using for loop, use Promise.each (or .map)

Look on the Bluebird API docs here and search "example of static map:". With map is clearer to understand than docs for each

var Promise = require('bluebird')
// promisify the entire mongoose Model
var Message = Promise.promisifyAll(Models.Message)

Promise.each(repliesIDsArray, function(replyID){
    return Message.findOneAsync({'_id': req.params.message_id})
        .then(function(doc){
            // do stuff with 'doc' here.  
        })
})

From the docs, .each (or .map) takes "an array, or a promise of an array, which contains promises (or a mix of promises and values)", so that means you can use it with array of 100% pure values to kickoff promise chain

Hope it helps!

来源：https://stackoverflow.com/questions/25110099/bluebird-promisfy-each-with-for-loops-and-if-statements

标签

node.js

mongoose

promise

node-mongodb-native

bluebird