garysweaver/activerecord-define_nils

Allows you to redefine what is translated to nil on read and what is stored instead of nil for specified attributes.

Define Nils for ActiveRecord 3.x/4.x and Rails 3.x/4.x

If working with a legacy database used by another application that uses a non-null value to mean null, you may need to translate certain values to nil to make them more normal to work with in Ruby/Rails and then save nil as a specific value.

For example, if nil is stored as 0 in my_id:

define_nils as: 0, for: :my_id

If nil is stored as 0 in my_id and your_id:

define_nils as: 0, for: [:my_id, :your_id]

If you want to accept 0 or '' as nil for my_id but save nil as 0:

define_nils as: [0, ''], for: :my_id, saving_as: 0

It will choose the only/first element in the as if you don't specify saving_as, so a less clear way to define that is:

define_nils as: [0, ''], for: :my_id

If you want to accept 0 or '' as nil for my_id and your_id but save nil as nil/null:

define_nils as: [0, ''], for: [:my_id, :your_id], saving_as: nil

It handles read_attribute calls, calls to the attribute name, and all belongs_to associations defined after the define_nils that use the specified attribute as a foreign_key. It also will show the value as nil in calls to inspect/returned values in rails console. So, for the most part it should look as if the value is nil within Ruby but on the database-side, nil is stored as whatever value you want to represent nil.

Setup

In your ActiveRecord/Rails 3.1+ project, add this to your Gemfile:

gem 'activerecord-define_nils'

Then run:

bundle install

Usage

If you are on Rails, the concern ActiveRecordDefineNils::Model is included automatically in ActiveRecord::Base via railtie.

Be sure to place define_nils above your belongs_to associations in the model class or those associations will query on unaltered foreign key values, which is probably not what you want.

Authors

This was written by FineLine Prototyping, Inc. by the following contributors:

• Gary Weaver (https://github.com/garysweaver)

License

Copyright (c) 2013 FineLine Prototyping, Inc., released under the MIT license.