Datamapper DataMapper

class Account

include DataMapper::Resource

property :id,  Serial
property :name, String
property :balance, Integer
property :min_balance, Integer
property :type,  Discriminator

end

class CurrentAccount < Account

validates_with_block :balance, if => lambda { |a| a.min_balance} do
    balance > min_balance  #validation block
end

end

In the above example :if block invoked after invoking actual validation. :if block should be called first and if its true than only validation block should be invoked.

Above example works fine if I replace validates_with_block with validates_with_method and move my validation logic to a method.