```ruby
module Viewable
  extend ActiveSupport::Concern

  included do
    has_many :views, class_name: self.name + 'View', dependent: :destroy

    def mark_read(user, at_time=nil, force=false)
      view = view_for(user)
      return true if view.ignored

      if view.new_record?
        view.read_at = at_time
        return view.save
      end

      return view.update_attributes(read_at: Time.now) unless at_time.present?
      return true if at_time <= view.read_at && !force
      view.update_attributes(read_at: at_time)
    end

    def ignore(user)
      view_for(user).update_attributes(ignored: true)
    end

    def unignore(user)
      view_for(user).update_attributes(ignored: false)
    end

    def ignored_by?(user)
      view_for(user).ignored
    end

    def last_read(user)
      view_for(user).read_at
    end

    def reload
      @view = nil
      super
    end

    private

    def view_for(user)
      @view ||= views.where(user_id: user.id).first_or_initialize
    end
  end
end
```

Throw in a sanity check for Viewable's view_for caching
user
```ruby
module Viewable
  extend ActiveSupport::Concern

  included do
    has_many :views, class_name: self.name + 'View', dependent: :destroy

    def mark_read(user, at_time=nil, force=false)
      view = view_for(user)
      return true if view.ignored

      if view.new_record?
        view.read_at = at_time
        return view.save
      end

      return view.update_attributes(read_at: Time.now) unless at_time.present?
      return true if at_time <= view.read_at && !force
      view.update_attributes(read_at: at_time)
    end

    def ignore(user)
      view_for(user).update_attributes(ignored: true)
    end

    def unignore(user)
      view_for(user).update_attributes(ignored: false)
    end

    def ignored_by?(user)
      view_for(user).ignored
    end

    def last_read(user)
      view_for(user).read_at
    end

    def reload
      @view = nil
      super
    end

    private

    def view_for(user)
      raise("view_for(#{user.id}) but @view.user_id is #{@view.user_id}") if @view && user.id != @view.user_id
      @view ||= views.where(user_id: user.id).first_or_initialize
    end
  end
end
```
assistant