# Categories like ebay

**URL:** <https://www.ruby-forum.com/t/categories-like-ebay/103912>\
**Category:** Rails\
**Created:** [May 11, 2007, 5:04pm UTC](https://www.ruby-forum.com/t/categories-like-ebay/103912 "2007-05-11T17:04:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![xain](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/x/82dd89/32.png) [@xain](https://www.ruby-forum.com/u/xain)\
**Post date:** [May 11, 2007, 5:04pm UTC](https://www.ruby-forum.com/t/categories-like-ebay/103912/1 "2007-05-11T17:04:13Z")

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I think the category feature of eBay is very handy. I want to figure out  
a way to to make this function work on rails.

What is so sepcial with ebay’s category feature?  
Let’s say we are going to buy a Movie DVD.  
HOME-\>BUY-\>DVDs & Movies  
in ‘Categories within DVDs & Movies’, click the first item ‘DVD, HD DVD  
& Blu-ray’. ok, now its fancy categories for dvd movie is ready, right  
on the left sidebar.

isn’t it different?

1. It has multiple category systems: movies are divided by their Format,  
Genre(with subgenres), Rating and Condition.
2. This multiple category systems are interactive. If you go deep to one  
category system’s subcategory, for instance we click PG-13(under Rating  
category), the other category system stay on sidebar, only now all  
categories show movies that is rated PG-13. (if any category doesn’t  
have any movies rated PG-13, this category removed)
3. A number is shown besides every category name to indicate how many  
movies’ are below this category.

This is a very useful system to help you pick out the very few movies  
that you love from more than 200,000 choices…

Is it hard to do it on Rails?