growstuff/app/models/seed.rb

class Seed < ActiveRecord::Base
  extend FriendlyId
  friendly_id :seed_slug, use: :slugged

  attr_accessible :owner_id, :crop_id, :description, :quantity, :plant_before, 
    :tradable_to, :slug

  belongs_to :crop
  belongs_to :owner, :class_name => 'Member', :foreign_key => 'owner_id'

  default_scope order("created_at desc")

  validates :quantity,
    :numericality => { :only_integer => true },
    :allow_nil => true

  scope :tradable, where("tradable_to != 'nowhere'")

  TRADABLE_TO_VALUES = %w(nowhere locally nationally internationally)
  validates :tradable_to, :inclusion => { :in => TRADABLE_TO_VALUES,
        :message => "You may only trade seed nowhere, locally, nationally, or internationally" },
        :allow_nil => false,
        :allow_blank => false

  def tradable?
    if self.tradable_to == 'nowhere'
      return false
    else
      return true
    end
  end

  def seed_slug
    "#{owner.login_name}-#{crop.system_name}".downcase.gsub(' ', '-')
  end
end