Returns an Awaitable of Vector of ResultOrExceptionWrapper after a filtering operation has been applied to each value in the provided KeyedTraversable

namespace HH\Asio;

function vfw<Tk, T>(
  KeyedTraversable<Tk, T, mixed> $inputs,
  (function(T): Awaitable<bool>) $callable,
): Awaitable<Vector<ResultOrExceptionWrapper<T>>>;

This function is similar to vf(), except the Vector in the returned Awaitable contains ResultOrExceptionWrappers instead of raw values.

This function is similar to Vector::filter(), but the mapping of the values is done using Awaitables.

This function is called vfw because we are returning a vector, doing a filtering operation and each member of the Vector is wrapped by a ResultOrExceptionWrapper.

$callable must return an Awaitable of bool.

The ResultOrExceptionWrappers in the Vector of the returned Awaitable are not available until you await or join the returned Awaitable.




// Return all non-negative odd numbers
// Positive evens filtered out,
// Negatives and zero cause exception
$odds = \HH\Asio\join(\HH\Asio\vfw(
  Vector {-1, 0, 1, 2, 3, 4},

  async ($val) ==> {
    if ($val <= 0) {
      throw new \Exception("$val is non-positive");
    } else {
      return ($val % 2) == 1;

foreach ($odds as $result) {
  if ($result->isSucceeded()) {
    echo "Success: ";
  } else {
    echo "Failed: ";
Failed: string(18) "-1 is non-positive"
Failed: string(17) "0 is non-positive"
Success: int(1)
Success: int(3)