How to print the integer difference of two columns (Rails 3.2.13) -

i'm very, new @ ruby on rails. don't know enough search answer. understand if hate me if please find in heart throw me teeniest, tiniest bone.

here database

activerecord::schema.define(:version => 20130502193545) do

create_table "employees", :force => true |t|
t.string "first_name"
t.string "last_name"
t.integer "employee_id"
t.date "hire_date"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
t.integer "sick_days"
t.integer "vacation_days"
t.integer "sick_days_used"
t.integer "vacation_days_used"
end

end

i want figure out how have "sick_days" , "sick_days_used" talk each other, "vacation_days" , "vacation_days_used". simple x - y equation can print on page how many vacation , sick days still available.

thank boundless patience such newbie.

you can add pure ruby methods on employee model calculate , returns differences.

class employee < activerecord::base   def remaining_sick_days     sick_days - sick_days_used   end    def remaining_vacation_days     vacation_days - vacation_days_used   end end 

when employee loaded can remaining vacations days @employee.remaining_vacation_days.