render_to_string from a rake task

Question

I want to use a Rake task to cache my sitemap so that requests for sitemap.xml won't take forever. Here's what I have so far:

  @posts = Post.all

  sitemap = render_to_string :template => 'sitemap/sitemap', :locals => {:posts => @posts}, :layout => false
  Rails.cache.write('sitemap', sitemap)

But when I try to run this, I get an error:

undefined local variable or method `headers' for #<Object:0x100177298>

How can I render a template to a string from within Rake?

Answer 1

There is a post about how to be able to access ActionView::Base methods and context from rake task.

However, this is a monkeypatch. Why not use the rails' cache mechanism to accomplish caching? :)

Later edit: The render_to_string function is defined in ActionController::Base context.

Below is a solution on how to make it work from rake tasks, taken from omninerd.

# In a rake task:
av = ActionView::Base.new(Rails::Configuration.new.view_path)
Rails.cache.write(
  "cache_var", 
  av.render(
    :partial => "view_folder/some_partial", 
    :locals => {:a_var => @some_var}
  )
)

Answer 2

Here's how I did it:

  av = ActionView::Base.new(Rails::Configuration.new.view_path)
  av.class_eval do
    include ApplicationHelper
  end

  include ActionController::UrlWriter
  default_url_options[:host] = 'mysite.com'

  posts = Post.all

  sitemap = av.render 'sitemap/sitemap', :posts => posts
  Rails.cache.write('sitemap', sitemap)

Note that I converted my template to a partial to make this work