Overview

Dase gem provides 'includes_count_of' method on a relation, which works similar to ActiveRecord's 'includes' method.

Calling 'includes_count_of(:articles)' on a relation object adds 'articles_count' method to each of the authors:

  authors = Author.includes(:publisher).includes_count_of(:articles, :conditions => {:year => 2012})  
  authors.first.name             # => 'Billy'                
  authors.first.articles_count   # => 2                

Installation

Add this line to your Rails 3.2.x application's Gemfile:

gem 'dase', "~> 3.2.4"

Usage

Basic usage:

  class Author
    has_many :articles
  end

  Author.includes_count_of(:articles).find_each do |author|
    puts "#{author.name} has #{author.articles_count} articles published"
  end

Using :conditions hash

Specify a hash of options which will be passed to the underlying finder which retrieves the association. Valid keys are: :conditions, :group, :having, :joins, :include

Author.includes_count_of(:articles, :conditions => {:year => 2012})   # counts only articles in year 2012

Using scope merging

class Article
  belongs_to :author
  scope this_year, lambda { where(:year => 2012) }
end 

results = Author.includes_count_of(:articles, :only => Article.this_year)   
results.first.articles_count  # => # number of articles of given Author for year 2012 only

This is achieved by merging the association scope with the scope provided as ":only => ..." option. No additional checks are performed, and providing the association of proper type is solely your responsibility.

Renaming counter column

sites = WebSite.includes_count_of(:users, :conditions => {:role => 'admin'}, :as => :admins_count)   
sites.each { |site| puts "Site #{site.url} has #{site.admins_count} admin users" }

Compatibility

Rails versions

This gem is for Rails 3.2.x . Earlier versions are not supported.

Note: the Dase gem version number correlates with the Active Record's versions number, which it has been tested with. E.g. the latest 3.2.* version of Dase will play nicely with the latest 3.2.* version of Active Record. Since dase gem is a sort of a "hack", make sure you specified the version number for "dase" gem in your Gemfile.

Polymorphic associations and HasManyThrough associations

Polymorphic associations and HasManyThrough associations support should work, but it is not tested quite well. Bug reports and pull requests are very welcome.

jRuby support

Not yet

How it works

Here's a pseudo-code that gives an idea on how it works internally

  counters_hash = Article.where(:year => 2012).count(:group => :author_id)
  Author.find_each do |author|
    puts "#{author.name} has #{counters_hash[author.id] || 0} articles published"
  end

Name origin

The gem is named by the german mathematician Johann Dase, who was a mental calculator - he could count and multiply numbers very quickly.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request