Module Attribute behaviour during compilation

Questions & Help Questions
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5

For note, module attributes are a lot like normal bindings, just saving you from typing the unquote part.

So this:

defmodule ModuleAttribute do
  @thing 1
  @thing 2
  def blah(), do: @thing # returns 2
  @thing 3
end

Is the same as this:

defmodule ModuleAttribute do
  thing = 1
  thing = 2
  def blah(), do: unquote(thing) # returns 2
  thing = 3
end

And thus this with an accumulated attribute:

defmodule ModuleAttribute do
  Module.register_attribute(__MODULE__, :thing, accumulate: true)
  @thing 1
  @thing 2
  def blah(), do: @thing # returns [2, 1]
  @thing 3
end

Is the same as this:

defmodule ModuleAttribute do
  thing = []
  thing = [1 | thing]
  thing = [2 | thing] # So this is now [2, 1]
  def blah(), do: unquote(thing) # returns [2, 1]
  thing = [3 | thing]
end