hello.rb

class Bar
  def calls
    ['a','b','c','d'].each do|i|
      yield i
    end
  end

  def hello
    self.calls do|call|
      puts call
    end
  end
end

Bar.new.hello

def new_calls(&block)
  ['z','y','x'].each do|i|
    yield i
  end
end

bar = Bar.new
bar.instance_eval do
  def calls(&block)
    new_calls(&block)
  end
end
bar.hello