Getting grand children of an instance

Question

I have associations set up so that a Category has many Posts and each Post has many Comments:

Category → Post → Comment

Having an instance of Category , how do one get all comments ?

I've tried this:

const posts = await category.getPosts()
const comments = await posts.map(post => post.getComments())

But the returned comments is only an array of Promises :

[ Promise {
  _bitField: 0,
  _fulfillmentHandler0: undefined,
  _rejectionHandler0: undefined,
  _promise0: undefined,
  _receiver0: undefined },
  ...

Answer 1

If the value of the expression following the await operator is not a Promise, it's converted to a resolved Promise.

This is what happening in your case. posts.map retruns an array which is not promise and hence await is resolving with the array of promises.

const posts = await category.getPosts()
const comments = await posts.map(post => post.getComments())

In the above logic posts.map is returning an array but not a promise. so to make it work you need to wrap that map in a Promise.all.

const posts = await category.getPosts()
const comments = await Promise.all(posts.map(post => post.getComments()))

Now when we print comments it will display array of the responses from all the resolved promises.