Active Record与Memcached的关联

Question

Hi for rails model association, i know i can do this:

For example a model class Page.

class Page < ActiveRecord::Base

 has_many :parts

end

I can do this:

Page.first.parts.find_by_name('body')

Page.first.parts.class actually returns Array. How can it activate methods for Part model? I found the similar post on How do rails association methods work?

My question is that when i try to use memcache to cache the response for parts methods. Then when i call Page.first.parts.find_by_name('body'), it tells me that the Array doesn't have method find_by_name. How do i solve this problem? I need to have the cache as this is one heavily used methods.

class Page
  def parts_with_cache
    Rails.cache.fetch("parts_for_page_#{id}", {:expires_in => 1.minutes}) do 
      parts_without_cache
    end
  end
  alias_method_chain :parts, :cache
end

Answer 1

由于您要获取与Page对象相关联的Parts对象数组，而该数组未按零件名称过滤，因此只需对结果集执行Array select方法。

body_parts = Page.first.parts.select{ |part| part.name == 'body' }