From: Phrogz <phrogz@...>
Date: 2010-03-31T13:31:33+09:00
Subject: Pop Quiz: aliasing versus wrapping

Below are two files that differ only in the 2nd line of code in each.
Can you guess what difference they will reveal? I must admit I was
surprised when I ran into this.

$ cat alias.rb
  class Object
    alias_method :to_js, :inspect
  end

  class Array
    def to_js; "[#{map{|o|o.to_js}.join(',')}]"; end
  end

  class Hash
    def to_js
      "{#{map{|k,v| "#{k.to_s.to_js}:#{v.to_js}" }.join(',')}}"
    end
  end

  [ 1, [true], {a:"foo"} ].each{ |o| puts o.to_js }

$ cat wrapped.rb
  class Object
    def to_js; inspect; end
  end

  class Array
    def to_js; "[#{map{|o|o.to_js}.join(',')}]"; end
  end

  class Hash
    def to_js
      "{#{map{|k,v| "#{k.to_s.to_js}:#{v.to_js}" }.join(',')}}"
    end
  end

  [ 1, [true], {a:"foo"} ].each{ |o| puts o.to_js }