Elixir Protocols Unveiled: A Guide to Writing and Using Protocols

In the world of Elixir, protocols serve as a gateway to achieve polymorphism and dynamic dispatch, allowing you to define and implement behaviors for different types. This guide will unveil the magic of Elixir protocols, demonstrating how to define them and provide implementations for diverse data types.

Define a Protocol

To define a protocol, we use the defprotocol macro. Let's create a Triple protocol with a single function, triple:

defprotocol Triple do
  def triple(input)
end

This protocol declares the triple function, and different types can provide their own implementations.

Implement the Protocol

Now, let's implement the Triple protocol for two different types: Integer and List. We use the defimpl macro for this:

defimpl Triple, for: Integer do
  def triple(int) do
    int * 3
  end
end
 
defimpl Triple, for: List do
  def triple(list) do
    list ++ list ++ list
  end
end

Here, we provide implementations for the triple function for both integers and lists.

Usage

Load the code into IEx and witness the dynamic dispatch in action:

iex> Triple.triple(3)
9
 
iex> Triple.triple([1, 2])
[1, 2, 1, 2, 1, 2]

By calling Triple.triple with different types, Elixir dynamically dispatches to the appropriate implementation, showcasing the power and flexibility of protocols.

Embrace Elixir protocols to write more flexible and maintainable code, where behaviors can be extended for various data types without compromising clarity and coherence.