Creates a promise that is resolved using a generator that yields values or
promises (somewhat similar to C#'s async keyword).

When called, the coroutine function will start an instance of the generator
and returns a promise that is fulfilled with its final yielded value.

Control is returned back to the generator when the yielded promise settles.
This can lead to less verbose code when doing lots of sequential async calls
with minimal processing in between.

use GuzzleHttp\Promise;

function createPromise($value) {
    return new Promise\FulfilledPromise($value);

$promise = Promise\coroutine(function () {
    $value = (yield createPromise('a'));
    try {
        $value = (yield createPromise($value . 'b'));
    } catch (\Exception $e) {
        // The promise was rejected.
    yield $value . 'c';

// Outputs "abc"
$promise->then(function ($v) { echo $v; });
public GuzzleHttp\Promise\PromiseInterface::FULFILLED = 'fulfilled'
public GuzzleHttp\Promise\PromiseInterface::PENDING = 'pending'
public GuzzleHttp\Promise\PromiseInterface::REJECTED = 'rejected'
public __construct(callable $generatorFn)
public _handleFailure( $reason)
  • internal
public _handleSuccess( $value)
  • internal
public cancel()
public getState()
public otherwise(callable $onRejected)
public reject( $reason)
public resolve( $value)
public then(?callable $onFulfilled = NULL, ?callable $onRejected = NULL)
public wait( $unwrap = true)
private $currentPromise
  • var PromiseInterface|null
private $generator
  • var Generator
private $result
private nextCoroutine( $yielded)
© 2020 Bruce Wells
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