Elixir — Dynamic Import

This won’t work in Elixir

alias Application.get_env(:app_name, :my_mod)

Solution

As you cannot import directly, you can do it through __using__ functionality provided.

So create a MyMod function and in __using__ function of this module alias it.

Why quote/unquote required

You can learn about quote/unquote here.

Brief Explanation

The building block of an Elixir program is a tuple with three elements. For example, the function call sum(1, 2, 3) is represented internally as:

{:sum, [], [1, 2, 3]}

You can get the representation of any expression by using the quote macro.

iex> quote do: sum(1, 2, 3)
{:sum, [], [1, 2, 3]}

But if you put variable in quote you will get result like

iex> number = 13
iex> quote do: sum(1, 2, number)
{:sum, [], [1, 2, {:number, [], Elixir}]}

To fix this you require unqoute

iex> number = 13
iex> quote do: sum(1, 2, unquote(number))
{:sum, [], [1, 2, 13]}