How to apply new validation for a domain field on grails

Question

I've this domain:

class Foo {
  static hasMany=[
    bars: Bar
  ]

  String name

  static constraints = {
    name(blank: false, unique: true)
  }
}

after inserting values to database I added another validation for bars

bars(nullable: false, validator: {value, object ->
            if(value.isEmpty()){
               return['bars.empty.validation.error']
            }
        })

now when i try to update Foo instances that were saved with no bars save is complaining on field bars :

Field error in object 'Foo' on field 'bars': rejected value [[Bar : (unsaved)]]

My question is how can I update Foo instances with no bars

Answer 1

You could change your custom validation to only apply to instances that don't have an id associated with them (indicating they are being inserted and not updated). Such as this:

bars(nullable: false, validator: {value, object ->
  if (object?.id) return // don't apply to previously saved instance.
  if(value.isEmpty()){
    return['bars.empty.validation.error']
  }
})