Nil in

About Nil

Nil is an English word meaning "nothing" or "zero". In Elixir, nil is a special value that means an absence of a value.

# I do not have a favorite color
favorite_color = nil

nil is an atom, but it is usually written as nil, not :nil. The boolean values true and false are atoms too.

nil === :nil
# => true

true === :true
# => true

You can check if a variable's value is nil using ==, with pattern matching, or using the is_nil guard.

def call(phone_number) do
  if phone_number == nil do
    :error
  end
end

def call(phone_number) when is_nil(phone_number) do
  :error
end

def call(nil) do
  :error
end