allowing objects to specify exception types

gistfile1.rb

class Share
  def call
    list.each do |address|
      referral = new_referral(address)

      # All else being equal, I'd probably prefer a caller-specified
      # fallback strategy
      referral.save do
        @unsaved << referral
      end
    end
  end
  
  def new_referral(address)
    Referral.new(address)
  end
end

class Referral
  class Invalid < StandardError; end
  
  def save
    # ... 
    # if invalid:
    if block_given? then yield else raise Invalid end
  end
end

Thanks for your thoughts on this!