How to cache tags with acts_as_taggable_on?

Question

I have model with tag context:

class Product < ActiveRecord::Base
  acts_as_taggable_on :categories
end

I'm trying to initialize tags caching:

class AddCachedCategoryListToProducts < ActiveRecord::Migration
  def self.up
    add_column :products,  :cached_category_list, :string
    Product.reset_column_information
    products = Product.all
    products.each { |p| p.save_cached_tag_list }
  end
end

But cached_category_list does not initializing. What I'm doing wrong? Does anybody can use caching with this gem (my version is 2.0.6)?

Answer 1

Well, today I had the same problem. I finally solved it, and my migration cached the desired tags. The problem with your migration was two-fold:

1. The ActsAsTaggable code which sets up caching needs to run again after the column information is reset. Otherwise, the caching methods are not created (see https://github.com/mbleigh/acts-as-taggable-on/blob/v2.0.6/lib/acts_as_taggable_on/acts_as_taggable_on/cache.rb)

2. The method you are calling, save_cached_tag_list, does NOT automatically save the record, as it is installed as a before_save hook, and it doesn't want to create an infinite loop. So you must call save.

So, try replacing your migration with the following, and it should work:

class AddCachedCategoryListToProducts < ActiveRecord::Migration
  def self.up
    add_column :products,  :cached_category_list, :string
    Product.reset_column_information
    # next line makes ActsAsTaggableOn see the new column and create cache methods
    ActsAsTaggableOn::Taggable::Cache.included(Product)
    Product.find_each(:batch_size => 1000) do |p|
      p.category_list # it seems you need to do this first to generate the list
      p.save! # you were missing the save line!
    end    
  end
end

That should do it.