= HasConstant

HasConstant is a gem to limit the values that a certain field may contain.
I find it very useful for multilingual sites to translate the values in forms and in the corresponding models.
It's also useful for pretty much any field in a model which is filled in from a select field or radio button.


Because HasConstant takes a list, and stores the select index in the model, it can be used to translate
the values.  Two important points to acheive this though; First of all, the two lists must be the same length,
so, if you are storing salutations 'Mr' and 'Mrs', then you must have the corresponding 'Herr' and 'Frau'
translations in your de locale file.  Also, you must always add any new values to the end of the list.

== Examples

class User < ActiveRecord::Base
  include HasConstant
  include HasConstant::Orm::ActiveRecord

  has_constant :salutations, lambda { I18n.t(:salutations) }
end

In the view

<% form_for @user || User.new do |form| %>
  <%= form.select :salutation, User.salutations -%>
  <%= form.submit 'submit' -%>
<% end %>

u = User.new(:salutation => 'Mrs')

u.salutation #=> 'Mrs'

I18n.locale = :de

u.salutation #=> 'Frau'

=== with ActiveRecord
class User < ActiveRecord::Base
  include HasConstant
  include HasConstant::Orm::ActiveRecord

  has_constant :salutations, ['Mr', 'Mrs']
end

User.salutations #=> ['Mr', 'Mrs']

u = User.new(:salutation => 'Dr')

u.salutation #=> nil

u.salutation = 'Mr'

u.salutation #=> 'Mr'

=== with Mongoid

class User
  include Mongoid::Document
  include HasConstant
  include HasConstant::Orm::Mongoid

  has_constant :industries, ['IT/Development', 'Marketing']
end

User.industries #=> ['IT/Development', 'Marketing']

=== without a database

class User
  include HasConstant

  has_constant :job_roles, ['Junior Developer', 'Developer', 'CTO', 'Other']
end

User.job_roles #=> ['Junior Developer', 'Developer', 'CTO', 'Other']

=== with a lambda or proc

class User
  include HasConstant

  has_constant :salutation, lambda { I18n.t(:salutations) }
  has_constant :industries, Proc.new { I18n.t(:industries) }
end

(assuming the correct translations exist)

I18n.locale = :en

User.salutations #=> ['Mr', 'Mrs']

I18n.locale = :de

User.salutations #=> ['Herr', 'Frau']

u = User.new(:salutation => 'Herr')

u.salutation #=> 'Herr'

I18n.locale = :en

u.salutation #=> 'Mr'

== with simple_form (http://github.com/plataformatec/simple_form)

<%= form.input :salutation, :collection => User.salutations -%>

== Note on Patches/Pull Requests
 
* Fork the project.
* Make your feature addition or bug fix.
* Add tests for it. This is important so I don't break it in a
  future version unintentionally.
* Commit, do not mess with rakefile, version, or history.
  (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
* Send me a pull request. Bonus points for topic branches.

== Copyright

Copyright (c) 2010 mattbeedle. See LICENSE for details.