wrapped_object.rb

class WrappedObject
  attr_reader :child

  def initialize(child, log = nil)
    @child = child
    @log = log || []
    @new_entry = nil
  end
  
  def record
    raise "No events to record" unless @new_entry
    @log << @new_entry
    @new_entry = nil
  end
  
  def log
    @log.map do |entry|
      args = entry[:args].empty? ? '' : '(' << entry[:args].map(&:inspect).join(', ') << ')'
      "#{entry[:method]}#{args}"
    end.join('.')
  end
  
  def method_missing(method, *args, &blk)
    # Only log if this doesn't throw an exception
    result = @child.public_send(method, *args, &blk)
    @new_entry = { :method => method, :args => args }
    WrappedObject.new(result, @log + [@new_entry])
  end
  
  def inspect
    @child.inspect
  end
  
  def to_s
    @child.to_s
   end
end

class Object
  def wrap
    WrappedObject.new(self)
  end
end


foo = "Test".wrap

foo.upcase!
# No, not quite right

foo.downcase!
# That's the one!
foo.record

foo = foo.gsub("t", "p")
# These get recorded anyway

# Show the log
puts foo.log

# Show the child
p foo