Saving multiple Mongoose objects with asyncjs not working

Question

I want to save two Mongoose objects in my mocha test - and be notified when both have succeeded. I am using the asyncjs library to achieve this.

beforeEach (done) ->

  obj1 = new Person({ name: 'Jon' })
  obj2 = new Person({ name: 'Dan' })

  console.log obj1   # ... { name: 'Jon', _id: 4534534543512 }

  async.list([
    obj1.save
    obj2.save
  ]).call().end( (err, res) ->
    return done(err) if err
    done()
  )

You can see that obj1 is being set to a MongoDB document in the console.log - but when I want to persist them to the db using the save function, I get the following error when trying to execute this:

TypeError: Cannot read property 'save' of undefined

If I were to replace the two functions in the async.list with say

console.log
console.log

The code executes fine ... Also, if I were to save the two objects outside the async.list function like so

obj1.save()
obj2.save()

It too executes fine with no errors.

I am stumped.

Also worth noting, is that there are two similarly named async libraries: async, and asyncjs. The above example is from asyncjs - but the better library is async, and the method to use there instead is: parallel. — Joerg
– Joerg, Commented Apr 5, 2013 at 6:46

Jonathan Lonowski · Accepted Answer · 2013-04-03 22:36:47Z

2

It's likely because the save functions aren't being called with a expected context (this).

When you pass a "method" like obj1.save, the reference async.list() gets is only to the function itself without any link back to obj1 (or obj2). It would be similar to:

save = obj1.save
save() # `this` is `undefined` or `global`

To pass with a fixed context, you can either bind them:

async.list([
  obj1.save.bind(obj1)
  obj2.save.bind(obj2)
]) # etc.

Or use additional functions so they're called after a member operator:

async.list([
  (done) -> obj1.save(done),
  (done) -> obj2.save(done)
]) # etc.

edited Apr 3, 2013 at 22:36

answered Apr 3, 2013 at 21:49

Jonathan Lonowski

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1 Comment

Joerg Over a year ago

That did the trick - thank you - you put an end to a lot of frustration. I suspected something around this - and passed this in via the call method - and called this.obj1.save(), which clearly didn't work.

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