behaviour_and_protocols.livemd

Untitled notebook

Section

# Behaviours and Protocols
defprotocol Printable do
  def to_csv(data)
end

# The defprotocol macro opens the definition of a protocol; inside, we define one or more 
# functions with its own arguments. 
# It is a sort of interface contract: we can say that every data type that is printable will have an 
# implementation for the to_csv function. 

defimpl Printable, for: Map do
  def to_csv(map) do
    Map.keys(map)
    |> Enum.map(fn k -> map[k] end)
    |> Enum.join(",")
  end
end

defimpl Printable, for: Integer do
  def to_csv(i) do
    to_string(i)
  end
end

Printable.to_csv(%{"a" => "b"})

# Behaviours
defmodule TalkingAnimal do
  @callback say(what :: String.t()) :: {:ok}
end

defmodule Cat do
  @behaviour TalkingAnimal
  def say(str) do
    "miaoo"
  end
end

Cat.say("")
# Code.eva

# ~r regexp w/interpolation
~W/words   interpolation/
~w/words   interpolation/