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"]

This should output 7, even though the case is different. Can I just override the equality method of the hash or something similar?

Thanks.

Answer 1

To prevent this change from completely breaking independent parts of your program (such as other ruby gems you are using), make a separate class for your insensitive hash.

class HashClod < Hash
  def [](key)
    super _insensitive(key)
  end

  def []=(key, value)
    super _insensitive(key), value
  end

  # Keeping it DRY.
  protected

  def _insensitive(key)
    key.respond_to?(:upcase) ? key.upcase : key
  end
end

you_insensitive = HashClod.new

you_insensitive['clod'] = 1
puts you_insensitive['cLoD']  # => 1

you_insensitive['CLod'] = 5
puts you_insensitive['clod']  # => 5

After overriding the assignment and retrieval functions, it’s pretty much cake. Creating a full replacement for Hash would require being more meticulous about handling the aliases and other functions (for example, #has_key? and #store) needed for a complete implementation. The pattern above can easily be extended to all these related methods.