Iterable

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Represents any entity that can be iterated over using something like foreach

The entity does not necessarily have to have a key, just values.

Iterable does not include arrays.

Guides

• Introduction
• Interfaces

Interface Synopsis

namespace HH;

interface Iterable implements Traversable<Tv>, \IteratorAggregate<Tv> {...}

Public Methods

• ->concat<Tu super Tv>(Traversable<Tu> $traversable): Iterable<Tu>
  Returns an Iterable that is the concatenation of the values of the current Iterable and the values of the provided Traversable
• ->filter((function(Tv): bool) $fn): Iterable<Tv>
  Returns an Iterable containing the values of the current Iterable that meet a supplied condition
• ->firstValue(): ?Tv
  Returns the first value in the current Iterable
• ->getIterator(): Iterator<Tv>
  Returns an iterator that points to beginning of the current Iterable
• ->lastValue(): ?Tv
  Returns the last value in the current Iterable
• ->lazy(): Iterable<Tv>
  Returns a lazy, access elements only when needed view of the current Iterable
• ->map<Tu>((function(Tv): Tu) $fn): Iterable<Tu>
  Returns an Iterable containing the values after an operation has been applied to each value in the current Iterable
• ->skip(int $n): Iterable<Tv>
  Returns an Iterable containing the values after the n-th element of the current Iterable
• ->skipWhile((function(Tv): bool) $fn): Iterable<Tv>
  Returns an Iterable containing the values of the current Iterable starting after and including the first value that produces true when passed to the specified callback
• ->slice(int $start, int $len): Iterable<Tv>
  Returns a subset of the current Iterable starting from a given key up to, but not including, the element at the provided length from the starting key
• ->take(int $n): Iterable<Tv>
  Returns an Iterable containing the first n values of the current Iterable
• ->takeWhile((function(Tv): bool) $fn): Iterable<Tv>
  Returns an Iterable containing the values of the current Iterable up to but not including the first value that produces false when passed to the specified callback
• ->toImmSet(): ImmSet<Tv>
  Returns an immutable set (ImmSet) converted from the current Iterable
• ->toImmVector(): ImmVector<Tv>
  Returns an immutable vector (ImmVector) converted from the current Iterable
• ->toValuesArray(): varray<Tv>
  Returns an array with the values from the current Iterable
• ->values(): Iterable<Tv>
  Returns an Iterable containing the current Iterable's values
• ->zip<Tu>(Traversable<Tu> $traversable): Iterable<Pair<Tv, Tu>>
  Returns an Iterable where each element is a Pair that combines the element of the current Iterable and the provided Traversable