Specs

get_and_update(
  t(),
  key(),
  (value() | nil -> {current_value, new_value :: value()} | :pop)
) :: {current_value, new_keywords :: t()}
when current_value: value()

Gets the value from key and updates it, all in one pass.

This fun argument receives the value of key (or nil if key is not present) and must return a two-element tuple: the current value (the retrieved value, which can be operated on before being returned) and the new value to be stored under key. The fun may also return :pop, implying the current value shall be removed from the keyword list and returned.

The returned value is a tuple with the current value returned by fun and a new keyword list with the updated value under key.

Examples

iex> Keyword.get_and_update([a: 1], :a, fn current_value ->
...>   {current_value, "new value!"}
...> end)
{1, [a: "new value!"]}

iex> Keyword.get_and_update([a: 1], :b, fn current_value ->
...>   {current_value, "new value!"}
...> end)
{nil, [b: "new value!", a: 1]}

iex> Keyword.get_and_update([a: 1], :a, fn _ -> :pop end)
{1, []}

iex> Keyword.get_and_update([a: 1], :b, fn _ -> :pop end)
{nil, [a: 1]}