From: Maurizio De Santis <desantis.maurizio@...>
Date: 2010-08-01T10:19:59+09:00
Subject: what is the correct way to extend native methods?

Hello!

suppose I want to modify Array.slice() (and consequentially, Array[]) in
order to accept a RegExp as argument, and return values matching the
regular expression. I tried to solve this problem in this way:


class Array

  def slice_with_regexp(*args)
    puts args
    return self.select{ |val| val.to_s =~ args[0] } if args.size == 1
and args[0].is_a?(RegExp)
  end

  alias_method :slice_without_regexp, :slice
  alias_method :slice, :slice_with_regexp

end

arr = %w[a b c]
puts arr.slice(/a/)


but executing this script I get this error:

(?-mix:a)
scripts.rb:8:in `slice_with_regexp': uninitialized constant RegExp
(NameError)
  from scripts.rb:17:in `<main>'

Surely I did something wrong, but the very question is: what is the
correct way to get the desired effect (that is:)

arr = %w[a b c]
puts arr[/a/]
=> ["a"]
puts arr.slice(/a/)
=> ["a"]

?
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