Modules and Functions in Elixir

Following the previous post you should be able to start an iex session and drop some Elixir lines in there.

Now we are gonna see how we can organize our code; A good way to achieve this is using Modules.

Let’s create a new file called animal.ex with the following code:

defmodule Animal do
  def make_sound(sound) do
    IO.puts(sound)
  end
end

There are a couple of things going on here so let’s see it line per line.

The first line is the module definition defmodule … do and for the name we usually go with CamelCase.

The second line defines a function inside the module, it should be pretty familiar if you know your ruby/python.

The third line prints to the terminal the given parameter here we don’t have a plain puts attached to a global object, instead we need to call the IO module and his puts method.

Now we can do:

iex animal.ex

That should pick our file, compile and then open the interactive shell:

Erlang/OTP 18 [erts-7.1] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Interactive Elixir (1.1.1) — press Ctrl+C to exit (type h() ENTER for help)

iex(1)>

Let’s go ahead and try the Animal module:

iex(1)> Animal.make_sound(‘cuack’)

cuack

:ok

Here we are calling the make_sound method of the Animal module, on the next line we have our message printed and the final line shows the IO.puts output ( we are gonna see more about that :ok later on)

That’s our first module there are some other ways to work with them like defining namespaces.

Let’s check some examples

defmodule Animal.Cat do
  def meow do
    IO.puts('meow')
  end
end

defmodule Animal.Dog do
  def bark do
   IO.puts('bark')
  end
end

If you are familiar with ruby this should be analogous to do Animal::Dog and Animal::Cat this it’s just to get our code in order between namespaces, we could also do

defmodule Animal do
  defmodule Dog do
    ...
  end
  
  defmodule Cat do
    ...
  end
end

and it should have the same effect.

Next post we are gonna check some other things about functions.