What is an atom in Elixir?

According to the Elixir documentation, an Atom is a constant whose value is own name. To some Ruby developers like me, an :atom is like a :symbol.

In Elixir, it is common to use atoms on lists, tuples, and maps:

defmodule Example do
  def example_params do
    # tupla
    tuple = {:ok, "This is a tuple"}

    # list
    list = [:slug, :title]

    # map
    map = %{
      name: "Diego",
      age: 35,
      country: "Brazil"
    }
  end
end

A curiosity in Elixir is that the boolean true and false also is :atoms:

iex> true == :true
> true

iex> false == :false
> false

iex> is_atom(false)
> true

iex> is_boolean(:false)
> true

In Elixir, we usually use atoms as a reference status for a given request:

defmodule ExampleController do
  #...

  def delete_person(conn, %{"id" => id}) do
    person = Person.get_person!(id)

    {:ok, _person} = Person.Repo.delete(person)

    conn
    |> put_flash(:info, "Person deleted successfully.")
    |> redirect(to: person_path(conn, :index))
  end
end

In the example above, the atom :ok indicates that the delete request was executed successfully. And then a "flash message" was triggered with status :info indicating that "the person was deleted successfully" and, after, redirected to :index.

I hope that this content helps and makes sense to you!

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