page_cache_directory is not initialized or set from config

[codev]

In Rails 3.2 page_cache_directory is initialized to app.config.paths["public"].first in:

https://github.com/rails/rails/blob/3-2-stable/actionpack/lib/action_controller/railtie.rb

But this doesn't seem the case in this gem. It is never given a default and the value is never copied over from config so the page_cache_directory variable is always blank.

This results in the gem trying to write pages to the root of my web server when upgrading to Rails 4.

[Xuhao]

I use this gem on my project which upgrade to rails4 form rails3.2.

The README is not correct, It does not work as it said.

Here is my solution:

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  include ActionController::Caching::Pages
  self.page_cache_directory = Rails.public_path
end