What is the best way to handle constants in Ruby when using Rails?

You can use an array or hash for this purpose (in your environment.rb):

OPTIONS = ['one', 'two', 'three']OPTIONS = {:one => 1, :two => 2, :three => 3}

or alternatively an enumeration class, which allows you to enumerate over your constants as well as the keys used to associate them:

class Enumeration  def Enumeration.add_item(key,value)    @hash ||= {}    @hash[key]=value  end  def Enumeration.const_missing(key)    @hash[key]  end     def Enumeration.each    @hash.each {|key,value| yield(key,value)}  end  def Enumeration.values    @hash.values || []  end  def Enumeration.keys    @hash.keys || []  end  def Enumeration.[](key)    @hash[key]  endend

which you can then derive from:

class Values < Enumeration  self.add_item(:RED, '#f00')  self.add_item(:GREEN, '#0f0')  self.add_item(:BLUE, '#00f')end

and use like this:

Values::RED    => '#f00'Values::GREEN  => '#0f0'Values::BLUE   => '#00f'Values.keys    => [:RED, :GREEN, :BLUE]Values.values  => ['#f00', '#0f0', '#00f']

I put them directly in the model class, like so:

class MyClass < ActiveRecord::Base  ACTIVE_STATUS = "active"  INACTIVE_STATUS = "inactive"  PENDING_STATUS = "pending"end

Then, when using the model from another class, I reference the constants

@model.status = MyClass::ACTIVE_STATUS@model.save

If it is driving model behavior, then the constants should be part of the model:

class Model < ActiveRecord::Base  ONE = 1  TWO = 2  validates_inclusion_of :value, :in => [ONE, TWO]end

This will allow you to use the built-in Rails functionality:

>> m=Model.new=> #<Model id: nil, value: nil, created_at: nil, updated_at: nil>>> m.valid?=> false>> m.value = 1=> 1>> m.valid?=> true

Alternatively, if your database supports enumerations, then you can use something like the Enum Column plugin.