Specs

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

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

fun is called with the current value under key in map (or nil if key is not present in map) 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 in the resulting new map. fun may also return :pop, which means the current value shall be removed from map and returned (making this function behave like Map.pop(map, key)).

The returned value is a two-element tuple with the current value returned by fun and a new map with the updated value under key.

Examples

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

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

iex> Map.get_and_update(%{a: 1}, :a, fn _ -> :pop end)
{1, %{}}

iex> Map.get_and_update(%{a: 1}, :b, fn _ -> :pop end)
{nil, %{a: 1}}