How do I create a hash in Ruby that compares strings, ignoring case?

Question

In Ruby, I want to store some stuff in a Hash, but I don\'t want it to be case-sensitive. So for example:

h = Hash.new
h[\"HELLO\"] = 7
puts h[\"hello\"]
         


        

Answer 1

If you really want to ignore case in both directions and handle all Hash methods like #has_key?, #fetch, #values_at, #delete, etc. , you'll need to do a little work if you want to build this from scratch, but if you create a new class that extends from class ActiveSupport::HashWithIndifferentAccess, you should be able to do it pretty easily like so:

require "active_support/hash_with_indifferent_access"

class CaseInsensitiveHash < HashWithIndifferentAccess
  # This method shouldn't need an override, but my tests say otherwise.
  def [](key)
    super convert_key(key)
  end

  protected

  def convert_key(key)
    key.respond_to?(:downcase) ? key.downcase : key
  end  
end

Here's some example behavior:

h = CaseInsensitiveHash.new
h["HELLO"] = 7
h.fetch("HELLO")                # => 7
h.fetch("hello")                # => 7
h["HELLO"]                      # => 7
h["hello"]                      # => 7
h.has_key?("hello")             # => true
h.values_at("hello", "HELLO")   # => [7, 7]
h.delete("hello")               # => 7
h["HELLO"]                      # => nil