Question

Hi I’m currently looking at a ruby quiz solution (http://rubyquiz.com/quiz76.html) and it makes sense to me, but I am having trouble understanding why there isn’t a self or any type of receiver for the methods shift, pop, scramble in munge_word:

class Array
  def munge_each
    map { |word| word.split(//).munge_word }
  end

  def munge_word
    first, last, middle = shift, pop, scramble
    "#{first}#{middle}#{last}"
  end

  def scramble
    sort_by{rand}
  end
end

Is it because it opened up the Array class and added functions to it? Are those methods class methods? I thought that syntax of var1, var2 = var3, var4 was just for concise multiple assignment of variables. I’ve never seen it done with methods on one side. Can someone explain?

Answer 1

first, last, middle = shift, pop, scramble

This is essentially equivalent to

first = shift
last = pop
middle = scramble

The receiver (for shift, pop and scramble methods) is implicit and it is self. Which is an instance of Array, because munge_word is an instance method.

I’ve never seen it done with methods on one side.

Variables, methods – it doesn’t matter. Right-hand values just need to be a list (or array) of expressions. Any expressions. Look:

x = 1

a, b = (x * 2), (x / 0 rescue 5)

a # => 2
b # => 5