setup

class Task < ActiveRecord::Base
  include Encoder
  
  code :status do
    Status::New      = "N"
    Status::Pending  = "P"
    Status::Finished = "F"
    Status::OverDue  = "O"
  end
  
  code :priority do
    Priority::High =  1
    Priority::Low =   5
  end
  
end

usage

t = Task.new # => #<Task id: nil, status: nil, priority: nil>

# Using a constant to assign the value
t.status = Task::Status::New # => "N"
t.status # => "N"
t.status.decode # => "New"

# Using a decoded value to assign the value
t.priority = 'high' # => "high"
t.priority # => "H"
t.priority.decode # => "High"

# Obtaining a list of the constant names defined for each attribute
Task::Status.constants # => ["Pending", "New", "OverDue", "Finished"]
Task::Priority.constants # => ["Low", "High"]