Overloading ActiveSupport's default to_sentence behaviour

Question

ActiveSupport offers the nice method to_sentence. Thus,

require 'active_support'
[1,2,3].to_sentence  # gives "1, 2, and 3"
[1,2,3].to_sentence(:last_word_connector => ' and ')  # gives "1, 2 and 3"

it's good that you can change the last word connector, because I prefer not to have the extra comma. but it takes so much extra text: 44 characters instead of 11!

the question: what's the most ruby-like way to change the default value of :last_word_connector to ' and '?

Answer 1

Well, it's localizable so you could just specify a default 'en' value of ' and ' for support.array.last_word_connector

See:

from: conversion.rb

def to_sentence(options = {})
...
   default_last_word_connector = I18n.translate(:'support.array.last_word_connector', :locale => options[:locale])
...
end

Step by step guide:

First, Create a rails project

rails i18n

Next, edit your en.yml file: vim config/locales/en.yml

en:
  support:
    array:
      last_word_connector: " and "

Finally, it works:

 
Loading development environment (Rails 2.3.3)
>> [1,2,3].to_sentence
=> "1, 2 and 3"

Answer 2

 class Array
   alias_method :old_to_sentence, :to_sentence
   def to_sentence(args={})
     a = {:last_word_connector => ' and '}
     a.update(args) if args
     old_to_sentence(a)
   end
 end

Answer 3

As an answer to how to override a method in general, a post here gives a nice way of doing it. It doesn't suffer from the same problems as the alias technique, as there isn't a leftover "old" method.

Here how you could use that technique with your original problem (tested with ruby 1.9)

class Array
  old_to_sentence = instance_method(:to_sentence)
  define_method(:to_sentence) { |options = {}|

    options[:last_word_connector] ||= " and "
    old_to_sentence.bind(self).call(options)
  }
end

You might also want read up on UnboundMethod if the above code is confusing. Note that old_to_sentence goes out of scope after the end statement, so it isn't a problem for future uses of Array.