DocumentationHSLReferenceFunctionHH\Lib\C\onlyx

HH\Lib\C\onlyx

Requires the Hack Standard Library to be installed.

Facebook Engineer?

This function is available as C\onlyx() in Facebook's www repository.

Returns the first and only element of the given Traversable, or throws if the Traversable is empty

namespace HH\Lib\C;

function onlyx<T>(
  Traversable<T> $traversable,
  ?\HH\Lib\Str\SprintfFormatString $format_string = NULL,
  mixed ...$format_args,
): T;

An optional format string (and format arguments) may be passed to specify a custom message for the exception in the error case.

For Traversables with more than one element, see C\firstx.

Time complexity: O(1) Space complexity: O(1)

Parameters

Traversable<T> $traversable
?\HH\Lib\Str\SprintfFormatString $format_string = NULL
mixed ...$format_args