Enforcing behaviors

One of the reserved module attributes in Elixir is @behaviour. It is used to ensure that a given module implements the required callbacks and that the module implements a given interface and behaves in a defined way.

How to do it…

To demonstrate the use of the @behaviour module attribute, follow these steps:

1. Create the Randomizer module inside the randomizer.ex file by adding the following code:

   defmodule Randomizer do
     use Behaviour
     defcallback randomize(low::Integer.t, high::Integer.t) :: Integer.t
   end

2. Create a module to implement the Randomizer behavior inside the my_module.ex file by adding the following code:

   defmodule MyModule do
     @behaviour Randomizer
   end

3. Open a new IEx session in the same directory where the modules defined in steps 1 and 2 are stored:

   > iex
   

4. Compile both modules starting with Randomizer:

   iex(1)> c("randomizer.ex")
   [Randomizer]
   iex(2)> c("my_module.ex")
   my_module.ex:1: warning: undefined behaviour function randomize/2 (for behaviour Randomizer...