# Counter cache

**URL:** <https://www.ruby-forum.com/t/counter-cache/138483>\
**Category:** Rails\
**Created:** [May 23, 2008, 3:02pm UTC](https://www.ruby-forum.com/t/counter-cache/138483 "2008-05-23T15:02:22Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Dmitrij\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/dfb087/32.png) [@Dmitrij\_S](https://www.ruby-forum.com/u/Dmitrij_S)\
**Post date:** [May 23, 2008, 3:02pm UTC](https://www.ruby-forum.com/t/counter-cache/138483/1 "2008-05-23T15:02:22Z")

</div>

class Category  
has\_many :clips  
end

class Clip  
belongs\_to :category, :counter\_cache = \> true

named\_scope :converted, :conditions =\> {:converted =\> true}  
end

1. How to update counters if clip changes its category\_id ?
2. How to implement custom counters by conditions, e.g:

category.clips\_count  
category.converted\_clips\_count