streaming_controller.rb

class StreamingController < ApplicationController
  class Writer
    def initialize(&blk)
      @blk = blk
    end

    def write(stuff)
      @blk.call(stuff)
      stuff.bytesize
    end
  end

  class EnumerableBody
    def initialize(&streaming_block_accepting_io)
      @streaming_block_accepting_io = streaming_block_accepting_io
    end

    def each(&blk)
      writer = Writer.new(&blk)
      @streaming_block_accepting_io.yield(writer)
    end
  end

  def index
    stream do |io|
      100.times {
        io.write "hello world\n"
      }
    end
  end

  def stream(&streaming_block_accepting_io)
    headers.delete("Content-Length")
    headers["Transfer-Encoding"] = "chunked"
    self.response_body = Rack::Chunked::Body.new(EnumerableBody.new(&streaming_block_accepting_io))
  end
end