Maps

Maps in Elixir are key-value stores. Maps can be created by using the %{} , Keys in a map can be of any type. The map data-structures are similar to keyword lists except they are unordered.

Try typing the following examples.

map = %{:msg => "Hello", "receiver" => :world}
map[:msg]
map["msg"]
map[:"msg"]

map["receiver"]
name = "Foo"
map = %{name => "world"}
map[name]

Nested data structures

Elixir provides a way for us to hold variables inside of maps. For instance, we can create a list of users that is a key-value map to another nested map:

iex> users = [
  john: %{name: "John", age: 27, languages: ["Erlang", "Ruby", "Elixir"]},
  mary: %{name: "Mary", age: 29, languages: ["Elixir", "F#", "Clojure"]}
]

We can then get variables using the [] and . syntax:

iex> users[:john].age # 27

We can then manipulate maps like so -

map = %{:msg => "Hello", "receiver" => :world}
%{map | msg: "goodbye"}
map.msg

Check out the Kernel module documentation for more information on other functions available to use when using nested data structures.