Question

What is the process of finding the documentation for a method in Ruby/Rails api http://api.rubyonrails.org/ .

Let’s take method ActiveRecord::Base.update as an example. It is used in one of the railscasts.

1. There is no mention of update in the api doc for the class
   http://api.rubyonrails.org/classes/ActiveRecord/Base.html
2. There’s
   nothing about update method in the source code for Base
   https://github.com/rails/rails/blob/0065f378262dc3f47880ce6211c7474bc7d11f0b/activerecord/lib/active_record/base.rb
3. In fact, I can’t even find this method in any classes included in
   ActiveRecord::Base.

I suspect this method is in ActiveRecord::Relation. However, I’m not sure.

I’m a beginner in Ruby/Rails, and I come from Java world, where I would normally expect to see all methods (inherited as well) in a javadoc for the class. What is the most effective finding relevant documentation for mixed-in/inherited methods in case of Ruby/Rails?

Thanks in advance!

Answer 1

You probably can’t find any good documentation about ActiveRecord::Base#update because the method has been deprecated since Rails version 2.3.8, according to APIdock..

The reason you can still use it is because it has been moved to ActiveRecord::Relation which can be seen in rails/activerecord/lib/active_record/relation.rb.

rails/activerecord/lib/active_record.rb contains all the autoloads for ActiveRecord which includes :Relation.

The documentation for ActiveRecord::Relation#update is as follows:

Updates an object (or multiple objects) and saves it to the database,
if validations pass. The resulting object is returned whether the
object was saved successfully to the database or not.

==== Parameters

• +id+ – This should be the id or an array of ids to be updated.
• +attributes+ – This should be a hash of attributes or an array of hashes.

==== Examples

# Updates one record 
Person.update(15, :user_name => 'Samuel', :group => 'expert')

# Updates multiple records 
people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }       
Person.update(people.keys, people.values)

EDIT: To answer your initial question, under most circumstances, doing a search on api.rubyonrails.org is enough to find the information you are looking for, as long as the information is up-to-date.

For potentially older API details, use apidock.com/rails. Doing a search there for ‘update’ actually shows both versions (::Base and ::Relation) and gives you details about each and what version of Rails each are used in.