From: Mark Somerville <ms@...>
Date: 2007-06-19T19:19:31+09:00
Subject: Class variables in class_eval

I'm confused, to say the least! I'm setting up caches on objects using a
class variable. It all works well until I try to extract it out to a module
to mixin to other objects:

module HostBasedCache
  def setup_cache(method, &method_proc)
    @@cache_method = method_proc if block_given?
    class_eval <<-METHOD
    def self.#{method}(param)
      #some stuff not relevant
      puts @@cache_method.call(param)
      #some stuff not relevant
    end
    METHOD
  end
end

class MyObject

extend HostBasedCache
setup_cache(:find_with_roles) do |id|
  User.find_by_id(id, :select => "users.id, roles.id", :include => [ :roles
])
end

end

Unfortunately, when calling find_with_roles I'm told that @@cache_method
isn't defined. Setting @@cache_method explicitly in MyObject (rather than the
setup_cache) call makes everything work. I must be missing some scoping
problem - can anyone explain this to me, please?

Thanks a lot,

Mark