Question

So I have a question of best practice in terms of extending functionality of common Ruby datatypes.

So Rails of course has a great method pluralize which takes a string and pluralizes it. What I’m particularly interested in is that you can call

"square".pluralize

and receive

=> "squares"

in return. What I want to do is a similar sort of thing — except for a Hash. For the sake of this question, let’s say I have a method pluralize_each which pluralizes each key and value of a hash.

def pluralize_each hash
  hash.each {|key,value| puts key.pluralize + "=>" + value.pluralize }
end

How can I manipulate this method so that I can call it on just a hash?
For example, I want to be able to call

{"cat" => "dog"}.pluralize_each
#=> {"cats" => "dogs"}

(Let’s forget that this particular method isn’t fully functional right now, with nested hashes and such.)

Is there any way to do this except for extending the Hash class? I would think that there would be a way.

Answer 1

With a module:

module HashPluralize
  def pluralize
    each { |key,value| puts "#{key.pluralize} => #{value.pluralize}" }
  end
end

Hash.send(:include, HashPluralize)

# Usage example:
{'user' => 'product'}.pluralize
users => products

---

EDIT: WHY?

@KL-7 legitimately asked a class edit vs module extension. This is my opinion:

If you are writing something organic, modules can be useful in order to optimize refactoring / code organization. Example:

module Pluralization

  def self.included(klass)
    klass.send :include, Pluralization.const_get(klass.to_s)
  rescue TypeError
    raise NotImplementedError.new("A pluralization method for the #{klass}" +
            " class is not supported at the moment")
  end

  module Array
    def pluralize
      'array pluralization implementation'
    end
  end

  module Hash
    def pluralize
      'hash pluralization implementation'
    end
  end

end

Array.send :include, Pluralization
Hash.send :include, Pluralization

puts Array.new.pluralize
puts Hash.new.pluralize

This module permits you to define a clean way to define pluralizations for various classes; you could add a configuration, separate the pluralization methods in various files, etc.

Anyway, if you just want to add a pluralize method to Hash class, there is no problem editing the Hash class (just ensure you are not overriding another method, with a method_defined? check f.e.)