Ruby case statements with multiple variables

Question

Ruby has a fairly powerful case..when..else construct for when you need to match criteria against a single variable. What is the "canonical" way to match criteria against multiple variables without simply nesting case statements?

Wrapping multiple variables in an array (like [x, y]) and matching against it isn't equivalent, because Ruby won't apply the magical case === operator to the elements of the array; the operator is only applied to the array itself.

I'm going to go ahead and respond with a community-wiki answer with a (defeated) stab at this question.

Answer 1

This is a simplistic way to add ===:

class Array
  def ===(other)
    return false if (other.size != self.size)

    other_dup = other.dup
    all? do |e|
      e === other_dup.shift
    end
  end
end

[
  ['foo', 3],
  %w[ foo bar ],
  %w[ one ],
  []
].each do |ary|

  ary_type = case ary
  when [String, Fixnum] then "[String, Fixnum]"
  when [String, String] then "[String, String]"
  when [String] then "[String]"
  else
    "no match"
  end

  puts ary_type

end

# >> [String, Fixnum]
# >> [String, String]
# >> [String]
# >> no match