fiber hack

fiber.rb

class Foo
  def initialize
    @closed = false
  end

  def close
    @closed = true
  end

  def closed?
    @closed
  end
end

module Defender
  def close(*args, **kwargs)
    Fiber.yield
    super(*args, **kwargs)
  end
end

def defer(obj)
  obj.extend Defender
  f = Fiber.new do
    yield
  end
  f.resume
  f
end

f = Foo.new

pp(closed: f.closed?) # false

d = defer(f){ p("block called"); f.close } # => "block called"

pp(closed: f.closed?) # false

d.resume

pp(closed: f.closed?) # true