CODEWITHSUNDEEP
javascriptnode.jsfunctionpromisebluebird
joshula
joshula

Reputation: 555

How do I promisify my own function?

How do I "promisify" my own function (that lives in another directory)? Here's my code:

// app.js

// include database
var mongo = require('./mongo');
var promise = require('bluebird');
var u = require('./util.js');
var mongo.connect = promise.promisify(require(mongo.connect));

// connect to database

var ago = new Date(new Date()-60000); // 10m ago
var scope = {size:0.01};

mongo.connect()
.then(
  mongo.endor.mapReduceAsync(u.mapTile, u.reduceTile,{
  out: {replace:'deathstar'}, scope:scope,
  query: {time:{$gte:ago}}, finalize:u.finalTile}))
.then(deathstar.find({},{fields:{_id:0, value: 1}})
  .toArray(function(err, docs){
    endor.insertAsync(_.map(docs, function(doc){return doc.value;}),{w:1});
  )
);

And here's the other file

// mongo.js

var promise = require('bluebird');
var mongodb = require('mongodb');
var MongoClient = mongodb.MongoClient;
promise.promisifyAll(mongodb);

module.exports.connect = promise.method(function(){
  // database environment
  var database;
    if (process.env.NODE_ENV == 'production'){database = pro;}
    else{database = database = dev;}
  module.exports.database = database;

  // connect to database
  return MongoClient.connectAsync(database)
    .then(function(db){
      module.exports.db = db;
      promise.all([
        db.createCollectionAsync('hoth', {w:1})
          .then(function(collection){
            collection.ensureIndexAsync()
              .then(function(index){
                module.exports.hoth = collection;
                console.log(index+' hoth');
              });
          }),
        db.createCollectionAsync('endor', {w:1})
          .then(function(collection){
            collection.ensureIndexAsync({})
              .then(function(index){
                module.exports.endor = collection;
                console.log(index+' endor');
              });
          }),
        db.createCollectionAsync('alderaan', {w:1})
          .then(function(collection){
            collection.ensureIndexAsync({time:-1, location:'2dsphere'})
              .then(function(index){
                module.exports.endor = collection;
                console.log(index+' alderaan');
              });
          })
      ]).then(function(){callback(null);});
    }
  );
});

and here's the error

/Users/Josh/Development/xWing/app.js:12
mongo.connectAsync()
  ^
TypeError: Object #<Object> has no method 'connectAsync'

Upvotes: 4

Views: 2501

Answers (1)

Benjamin Gruenbaum
Benjamin Gruenbaum

Reputation: 276496

Promises bring back the qualities of synchronous code.

Given your API is already promisified - You simply return a promise from your function and then use that.

module.exports.connect = Promise.method(function(){
    // do a bunch of stuff
    return mongo.connectAsync().then(...
});

Note the Promise.method bit isn't required, it just turns thrown errors into rejections to give you throw safety and makes sure you return a promise so it's best practice and guards you against mishaps.

Upvotes: 3

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