How do I add 'each' method to Ruby object (or should I extend Array)?

Question

I have an object Results that contains an array of result objects along with some cached statistics about the objects in the array. I\'d like the Results object to

Answer 1

If you create a class Results that inherit from Array, you will inherit all the functionality.

You can then supplement the methods that need change by redefining them, and you can call super for the old functionality.

For example:

class Results < Array
  # Additional functionality
  def best
    find {|result| result.is_really_good? }
  end

  # Array functionality that needs change
  def compact
    delete(ininteresting_result)
    super
  end
end

Alternatively, you can use the builtin library forwardable. This is particularly useful if you can't inherit from Array because you need to inherit from another class:

require 'forwardable'
class Results
  extend Forwardable
  def_delegator :@result_array, :<<, :each, :concat # etc...

  def best
    @result_array.find {|result| result.is_really_good? }
  end

  # Array functionality that needs change
  def compact
    @result_array.delete(ininteresting_result)
    @result_array.compact
    self
  end
end

In both of these forms, you can use it as you want:

r = Results.new
r << some_result
r.each do |result|
  # ...
end
r.compact
puts "Best result: #{r.best}"