有关创建自定义Sprockets处理器的文档？

Question

我正在尝试为Rails创建一个sprockets预处理器,它.png.rb在资源管道中查找文件,并使用它们在我的应用程序中生成各种页面的png屏幕截图.

我已经阅读了很多这个主题,但我似乎无法找到关于如何设置这个问题的任何直接文档.请帮忙？

这是我到目前为止所拥有的:

---

/initializers/sprockets.rb:

require 'screenshot_preprocessor'

Rails.application.assets.register_mime_type('screenshot/png', '.png.rb')
Rails.application.assets.register_preprocessor('screenshot/png', ScreenshotPreprocessor)

---

/lib/screenshot_preprocessor.rb:

class ScreenshotPreprocessor
  # What API do I need to provide here?
  #   - What methods do I need to provide?
  #   - What parameters does Sprockets pass me?
  #   - What do I need to return to Sprockets?
end

Answer 1

好的,我还不确定在哪里找到这方面的文件.但是,通过阅读Sprockets的源代码,使用pry调试器,以及阅读使用Sprockets做过类似事情的人的博客文章,我能够想出这个:

/initializers/sprockets.rb:

require 'screenshot_generator'

Rails.application.assets.register_engine('.screenshot', ScreenshotGenerator)

/lib/screenshot_generator.rb:

require_relative 'capybara_screenshot' # Don't worry about this, it's not
                                       # relevant to this question.

class ScreenshotGenerator < Sprockets::Processor
  def evaluate(context, locals)
    generator_class = ScreenshotGenerator.get_generator_class(context.pathname)

    return generator_class.new.generate
  end

  private

  def self.get_generator_class(generator_file)
    # This evaluates the Ruby code in the given file and returns a class that
    # can generate a binary string containing an image file.
    # (Code omitted for brevity)
  end
end

这对我来说现在很好用,但我真的更喜欢看一些关于Sprockets预处理器,后处理器和引擎如何工作的真实文档.如果有人发现任何此类文件,请发回答.