Modules

Remarks#

Module Names

In Elixir, module names such as IO or String are just atoms under the hood and are converted to the form :"Elixir.ModuleName" at compile time.

iex(1)> is_atom(IO)
true
iex(2)> IO == :"Elixir.IO"
true

List a module’s functions or macros

The __info__/1 function takes one of the following atoms:

• :functions - Returns a keyword list of public functions along with their arities
• :macros - Returns a keyword list of public macros along with their arities

To list the Kernel module’s functions:

iex> Kernel.__info__ :functions
[!=: 2, !==: 2, *: 2, +: 1, +: 2, ++: 2, -: 1, -: 2, --: 2, /: 2, <: 2, <=: 2,
 ==: 2, ===: 2, =~: 2, >: 2, >=: 2, abs: 1, apply: 2, apply: 3, binary_part: 3,
 bit_size: 1, byte_size: 1, div: 2, elem: 2, exit: 1, function_exported?: 3,
 get_and_update_in: 3, get_in: 2, hd: 1, inspect: 1, inspect: 2, is_atom: 1,
 is_binary: 1, is_bitstring: 1, is_boolean: 1, is_float: 1, is_function: 1,
 is_function: 2, is_integer: 1, is_list: 1, is_map: 1, is_number: 1, is_pid: 1,
 is_port: 1, is_reference: 1, is_tuple: 1, length: 1, macro_exported?: 3,
 make_ref: 0, ...]

Replace Kernel with any module of your choosing.

Using modules

Modules have four associated keywords to make using them in other modules: alias, import, use, and require.

alias will register a module under a different (usually shorter) name:

defmodule MyModule do
  # Will make this module available as `CoolFunctions`
  alias MyOtherModule.CoolFunctions
  # Or you can specify the name to use
  alias MyOtherModule.CoolFunctions, as: CoolFuncs
end

import will make all the functions in the module available with no name in front of them:

defmodule MyModule do
  import Enum
  def do_things(some_list) do
    # No need for the `Enum.` prefix
    join(some_list, " ")
  end
end

use allows a module to inject code into the current module - this is typically done as part of a framework that creates its own functions to make your module confirm to some behaviour.

require loads macros from the module so that they can be used.

Delegating functions to another module

Use defdelegate to define functions that delegate to functions of the same name defined in another module:

defmodule Math do
  defdelegate pi, to: :math
end


iex> Math.pi
3.141592653589793