Elixir - What does the 'use' keyword do?

Question

I suspect it's an elementary question, but it's been hard to find a succinct, canonical answer online.

From what little I understand;

• It's distinct from both 'require' and 'import'
• It's used to import the contents of modules.
• It's a macro

Can anyone clarify?

Answer 1

It requires the given module and then calls the __using__/1 callback on it allowing the module to inject some code into the current context. See https://elixir-lang.org/getting-started/alias-require-and-import.html#use.

Example:

defmodule Test do
  use Utility, argument: :value
end

is about the same as

defmodule Test do
  require Utility
  Utility.__using__(argument: :value)
end