ActsAsDefault

Using acts as default you can set a default row in your activerecord collection, also for has_many relationships

Installation

Add this line to your application's Gemfile:

gem 'acts_as_default'

And then execute:

$ bundle

Or install it yourself as:

$ gem install acts_as_default

Usage

Include ActsAsDefault in the models when you need a default row Call acts_as_default, specifying which field, is present to determine sub-collections

class Parent < ActiveRecord::Base
  include ActsAsDefault
  acts_as_default
  has_many :sons
end

class Son < ActiveRecord::Base
  include ActsAsDefault
  acts_as_default :parent_id
  belongs_to :parent
end

Then create a migration to create default column:

add_column :parents, :default, :boolean
add_column :sons, :default, :boolean

Using default value in the simple way:

p1 = Parent.new
p1.save!
p2 = Parent.new
p2.save!
p3 = Parent.new
p3.save!
puts p1.default #true, because was the first created
puts p2.default #false, because a default is already present
puts p3.default #false, because a default is already present

p3.destroy! #if we destroy a non default object nothing happens

p1.destroy! #but if we destroy the default object...
p2.reload #don't forget to reload to see changes
puts p2.default #true, now p2 is default, because was the only one present, in case of more the recent based on created_at will become the default

Setting the default manually

You can always call:

p1 = Parent.new
p2 = Parent.new

puts p1.default #true, because was the first created
puts p2.default #false, because a default is already present

model.set_as_default!

To immediately switch the object as default and save.

Using default value in the complex way:

You can use acts_as_default to manage default for collection in has_many relationships

p1 = Parent.new
p2 = Parent.new

s1 = Son.new
s1.parent = p1
s1.save!

s2 = Son.new
s2.parent = p1
s2.save!

s3 = Son.new
s3.parent = p2
s3.save!

puts s1.default #true, because was the first created for p1
puts s2.default #false, because a default is already present in p1
puts s3.default #true, because was the first created for p2

Contributing

Fork it ( http://github.com/MirkoMignini/acts_as_default/fork )
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request