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Question

rails: filter categories where there are at least one article

Answer 1

+1 A:

I think that counter cache is your friend here. Take a look here.

You can add the counter cache to the categories table and in the CategoryArticles you do like

class CategoryArticles
  belongs_to :article
  belongs_to :category, :counter_cache => true
end

So you can find your Category with

@categories = Category.find(:all, :conditions => ["category_articles_count > ?", 0])

Francisco 2010-10-05 08:41:02

Thats exactly what I needed! Do you know how I do it when I don't have the CategoryArticles Model by just implementing the has_and_belongs_to_many property?

Markus 2010-10-05 10:04:24

I'm not sure that you can do it with a `has_and_belong_to_many`. My suggestion is to do it like that. class CategoryArticles belongs_to :article belongs_to :category, :counter_cache => true end class Category has_many :articles, :through => :category_articles has_many :category_articles end class Article has_many :categories, :through => :category_articles has_many :category_articles end

Francisco 2010-10-05 11:11:21

Just saw that you cannot format the code in comments... you can take a look in this gist http://gist.github.com/611736

Francisco 2010-10-05 15:33:03

Ok, thanks a lot! I will change my schema then.

Markus 2010-10-05 16:48:04

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