Returns an Awaitable of Map of ResultOrExceptionWrapper after a filtering operation has been applied to each key/value pair in the provided KeyedTraversable

namespace HH\Asio;

function mfkw<Tk as arraykey, T>(
  KeyedTraversable<Tk, T> $inputs,
  (function(Tk, T): Awaitable<bool>) $callable,
): Awaitable<Map<Tk, ResultOrExceptionWrapper<T>>>;

This function is similar to mfk(), except the Map in the returned Awaitable contains values of ResultOrExceptionWrapper instead of raw values.

This function is similar to Map::filterWithKey(), but the filtering of the keys and values is done using Awaitables.

This function is called mfkw because we are returning a map, doing a filtering operation on keys and values, and each value member in the Map is wrapped by a ResultOrExceptionWrapper.

$callable must return an Awaitable of bool.

The ResultOrExceptionWrappers in the Map 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\mfkw(
  Map {
    '-one' => -1,
    'zero' => 0,
    'one' => 1,
    'two' => 2,
    'three' => 3,
    'four' => 4,

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

foreach ($odds as $num => $result) {
  if ($result->isSucceeded()) {
    echo "$num Success: ";
  } else {
    echo "$num Failed: ";
-one Failed: string(20) "-one is non-positive"
zero Failed: string(20) "zero is non-positive"
one Success: int(1)
three Success: int(3)