Inversion of control.rb

class SoundFile
  attr_reader :binaries
  delegate :info, :to => :binaries

  def initialize
     @binaries = Binaries.instance
  end
end

module Binaries
  class <<self
    def instance
      @instance ||=
        if windows?
          Windows.new
        else
          Nix.new
        end
    end
  end

  class Windows
    def info
      `./bin/sndfile-info.exe`
    end
  end

  class Nix
    def info
      `./bin/sndfile-info`
    end
  end
end