tier_membership.rb

class TierMembership < ActiveRecord::Base
  attr_accessible :tier, :user

  belongs_to :tier
  belongs_to :user

  validates :user_id,               presence: true
  validates :tier_id,               presence: true, uniqueness: { scope: :user_id }

  validate :valid_user_role

  def valid_user_role
    unless user.blank? || ["agent", "admin"].include?(user.account.role)
      errors.add(:user, "must be agent or admin")
    end
  end

end