futureToPromise

Converts a Future into a Promise.

This feature is experimental!

This API is still experimental, so it may change or be removed in future versions. You should not rely on it for production applications.

Signature

futureToPromise(aFuture)

Type(what is this?)

forall e, v:
  (Future e v) => Promise v e

Documentation

Converts a Future into a Promise.

Note that this conversion may not be as accurate due to the differences in Promise and Future semantics. In particular, Promises recursively flatten any object with a .then method, and do not have a separate representation for cancellations.

Cancelled futures are converted to rejected promises with a special Cancelled() object.

Example:

const futureToPromise = require('folktale/conversions/future-to-promise');
const Future = require('folktale/concurrency/future');

$ASSERT(
  (await futureToPromise(Future.of(1))) == 1
);

try {
  await futureToPromise(Future.rejected(1));
  throw 'never happens';
} catch (e) {
  $ASSERT(e == 1)
}

Properties

Source Code

Defined in source/conversions/future-to-promise.js at line 19, column 0

(aFuture) => {
  return new Promise((resolve, reject) => {
    aFuture.listen({
      onResolved: (value) => resolve(value),
      onRejected: (error) => reject(error),
      onCancelled: ()     => reject(Cancelled())
    });
  });
}