method

includes

v3.0.0 - Show latest stable - 1 note - Class: ActiveRecord::QueryMethods

includes(*args) public

No documentation

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# File activerecord/lib/active_record/relation/query_methods.rb, line 12
    def includes(*args)
      args.reject! { |a| a.blank? }
      clone.tap {|r| r.includes_values = (r.includes_values + args).flatten.uniq if args.present? }
    end

January 2, 2012 - (>= v3.0.0)

3 thanks

Links and basic explanation

This function, available on any Base derived class, allows eager loading. So when iterating over a result, all the data can be pre-cached, reducing the number of queries from 1+x to 2.

Several ways to use this include:

Post.includes(:author).where(..)

Post.includes([:author, :comments]).where(..)

Post.includes( :comments => :replies ).where(..)

The result is a Relation, so where and other function may be called.

.includes(:comments).to_a is the same as , .find(:all, :includes => :comments)

Some good documentation here: http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

Apperently one can get similar results by using joins, but i’m not expert on joins, so please ammend and read: http://guides.rubyonrails.org/active_record_querying.html

includes

Related methods

No documentation

Links and basic explanation