Elixir v1.0.4 Access protocol

The Access protocol is used by foo[bar] and also empowers the nested update functions in Kernel.

For instance, foo[bar] translates Access.get(foo, bar). Kernel.get_in/2, Kernel.put_in/3, Kernel.update_in/3 and Kernel.get_and_update_in/3 are also all powered by the Access protocol.

This protocol is implemented by default for keywords, maps and dictionary like types:

iex> keywords = [a: 1, b: 2]
iex> keywords[:a]
1

iex> map = %{a: 1, b: 2}
iex> map[:a]
1

iex> star_ratings = %{1.0 => "★", 1.5 => "★☆", 2.0 => "★★"}
iex> star_ratings[1.5]
"★☆"

The key comparison must be implemented using the === operator.

Summary

Functions

get(container, key)

Accesses the given key in the container

get_and_update(container, key, fun)

Gets a value and updates the given key in one pass

Types

t :: term

Functions

get(container, key)

Specs

get(t, term) :: t

Accesses the given key in the container.

get_and_update(container, key, fun)

Specs

get_and_update(t, term, (term -> {get, term})) :: {get, t} when get: var

Gets a value and updates the given key in one pass.

The function must receive the value for the given key (or nil if the key doesn’t exist in container) and the function must return a tuple containing the get value and the new value to be stored in the container.