CODEWITHSUNDEEP
node.jspromisebluebird
CarbonMan
CarbonMan

Reputation: 4490

bluebird .all() does not call .then

I have an unknown number of async processes that might run from a request. There is a block of text to be modified by these processes.

UpdateScript is called with the text to be modified, it has a callback that I would like to run when everything is complete.

var promise = require('bluebird');

function updateScript(text, cb){
   var funcChain = [],
      re = some_Regular_Expression,
      mods = {text: text};
   while (m = re.exec(mods.text)) {
      // The text is searched for keywords. If found a subprocess will fire
      ....
      funcChain.push( changeTitleAsync(keyword, mods) );
   }
   promise.all(funcChain)
   .then(function(){
      // This is never called.
      cb(mods.text);
   });
}

function changeTitle(encryptedId, mods){
   try{
       // database request modifies mods.text
   }catch(e){
     throw e;
   }
}
var changeTitleAsync = promise.promisify(changeTitle);

The changeTitle code is called but the "then" call is not

Upvotes: 1

Views: 408

Answers (1)

aarosil
aarosil

Reputation: 4898

Partly the problem is incorrect use of promisify(). This is meant to convert a node-style function that takes a callback as it's last argument into one that returns a promise (see docs here).

Instead what you can do with your function above is have it return a new Promise manually like this:

function changeTitle(encryptedId, mods) {
  return new Promise(function(resolve, reject){
    try {
      // do something then resolve promise with results
      var result = ...
      resolve(result)
    } catch (e) {
      // reject the promise with caught error
      reject(e)
    }
  })
}

HOWEVER There is one mistake above: I assume the db call to update the text is also asynchronous, sothe try /catch block will never catch anything because it will run through just as the db kicks off intially.

So what you would have to do is promisify the DB call itself. If you're using a node db library (like Mongoose, etc) you could run Promise.promisifyAll() against it, and use the Async versions of the functions (see promisifyAll section on above link for details).

Hope this helps!!

Upvotes: 2

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