[FLOSS Week]: enum_field

Posted by: Mathieu Martin on 2009-02-17

This release announcement is part of FLOSS week.

At GiraffeSoft, we love DRY code. That's why we're very quick at creating small plugins that encapsulate the way we code.

Today I'll unveil one such plugin. It's a very simple one that lets you specify an enum field for an ActiveRecord model.

The plugin of course encapsulates a standard validates_inclusion_of

class Computer < ActiveRecord::Base
  validates_inclusion_of :status, :in =>
    ['on', 'off', 'standby', 'sleep', 'out of this world']
  #...
end

But then it adds a few nifty extras that just make sense. So using the enum_field plugin:

class Computer < ActiveRecord::Base
  enum_field :status,
    ['on', 'off', 'standby', 'sleep', 'out of this world']
  #...
end

gives us a bunch useful things:

• add a validates_inclusion_of with a simple error message ("invalid #{field}")
• define the following query methods, in the name of expressive code:
  • on?
  • off?
  • standby?
  • sleep?
  • out_of_this_world?
• define the Computer::STATUSES constant, which contains all acceptable values

This plugin has been known to work very well with other plugins. For example, we've used it successfully with Phusion's excellent default_value_for plugin.

class Computer < ActiveRecord::Base
  enum_field :status,
    ['on', 'off', 'standby', 'sleep', 'out of this world']
  default_value_for :status, 'off'
  #...
end

If you don't like the default error message, you can of course override it with an additional :message option.

enum_field :status, 
  ['on', 'off', 'standby', 'sleep', 'out of this world'],
  :message => "incorrect status"

Get it

You can install it inside your app either as a plugin:

$ script/plugin install git://github.com/giraffesoft/enum_field.git

or as a gem, add the following line in you config/environment.rb:

config.gem "giraffesoft-enum_field", :lib => "enum_field", 
  :source => "http://gems.github.com"

or of course, fork it on GitHub

Conclusion

This is a good general purpose plugin to include in one's customized Rails app generator. We may add it to blank in the future, if we find we're frequently adding it to new projects.

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