ruby-hack-night.rb

#!/usr/bin/env ruby
# Ruby Project Night 2014-09-22 @ SUP46, Stockholm
# Why does the to_s methods yeild different results?
# What am I doing wrong and how should I do different?
#
# After a good nights sleep I still cannot wrap my head around this.
#
# ruby -v : ruby 2.0.0p353 (2013-11-22 revision 43784) [x86_64-linux]

# Internal list class
class List
  attr_reader :list

  def initialize(elem)
    @list = Array.new(elem)
  end

  # method 1
  def to_s
    @list.to_s
  end

  # method 2
  # def to_s
  #   @list
  # end
end

list = List.new(%w(1 2 3))

puts list         # method 1: ["1", "2", "3"]
                  # method 2: #<List:0x00000002587648>

puts list.list    # 1\n2\n3\n    <= these are actual newlines in console

Shorter example:

irb(main):023:0> puts %w(1 2 3)
1
2
3
=> nil
irb(main):024:0> puts %w(1 2 3).to_s
["1", "2", "3"]
=> nil
irb(main):025:0> puts %w(1 2 3).inspect
["1", "2", "3"]
=> nil

https://github.com/ruby/ruby/blob/d198d64e0464c141f70c49880bf511ac3dcd1162/io.c#L7097-L7126

If it is enumerable, and the value is a string, then it prints it with a newline.