# Where to define computed properties row-level?

1. define computed property as a let inside a collection in .kmongo.

   for example, to define age as a computed property:

   
   
   
   
   

    

   
   
   

   collection Employee {
   	property name:String
   	property designation:String
   	property dob:CalendarDate
   	let age:Int
   }
   

2. run command compile

3. implement the computation logic in the generated RowExtn class

   
   
   

    

   
   
   
   
   
   
   
   

   trait EmployeeRowExtn extends EmployeeRowExtnTrait {
     row: EmployeeRow =>
     override lazy val age: Int = {
       val today = grab[TimeService].todayAtLocal
       val ageInDays = dob.noOfDaysInFuture(today)
       val age = ageInDays / 365
       age
     }
   }