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Simple ActiveRecord plugin that allows to specify default values for attributes.

Just add gem 'attribute-defaults' to your Gemfile.

Alternatively, run sudo gem install attribute-defaults and add require 'attribute_defaults' to your app.

First, a simple case …

class Foo < ActiveRecord::Base
  attr_default :age, 18
  attr_default :last_seen do
    Time.now
  end
end
Foo.new # => age: 18, last_seen: '2010-09-15 10:30'

… or the same via mass-definition …

class Foo < ActiveRecord::Base
  attr_defaults :age => 18, :last_seen => lambda { Time.now }
end
Foo.new # => age: 18, last_seen: '2010-09-15 10:30'

It doesn’t override values that are already set …

class Foo < ActiveRecord::Base
  attr_defaults :age => 18
end
Foo.new(:age => 25) # => age: 25

… but allows you to set your own conditions e.g. blank? …

class Foo < ActiveRecord::Base
  attr_defaults  :numbers => { :default => [1], :if => :blank? }
end
Foo.new(:numbers => nil) # => numbers: [1]
Foo.new(:numbers => [])  # => numbers: [1]
Foo.new(:numbers => [2]) # => numbers: [2]

… and it respects protected attributes …

class Foo < ActiveRecord::Base
  attr_protected :age
  attr_defaults  :age => 18
end
Foo.new(:age => 25) # => age: 18

When attributes aren’t database columns …

class Foo < ActiveRecord::Base
  attr_accessor  :birth_year
  attr_defaults  :birth_year => lambda {|r| r.age ? Time.now.year - r.age : nil }
end
Foo.new(:age => 30) # => age: 30, birth_year: 1980

It works with persisted records …

# DB table 'foos': [{id: 1, age: NULL}, {id: 2, age: 25}]
class Foo < ActiveRecord::Base
  attr_defaults  :age => 18
end
Foo.all # => [{id: 1, age: 18}, {id: 2, age: 25}]

… or not …

class Foo < ActiveRecord::Base
  attr_defaults  :age => { :default => 18, :persisted => false }
end
Foo.all # => [{id: 1, age: nil}, {id: 2, age: 25}]

To specify a Hash as a default value, use …

class Foo < ActiveRecord::Base
  attr_accessor  :some_hash
  attr_default   :some_hash, :default => {}
end
Foo.new.some_hash # => {}

Inspired by the default_value_for plugin github.com/FooBarWidget/default_value_for

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.