class ActiveRecord::Reflection::AssociationReflection

def validate?

* the association is a +has_many+ association
* you use autosave; autosave: true
* you explicitly enable validation; validate: true

validate: false, validation will take place when:
Unless you explicitly disable validation with

the parent's validation.
Returns whether or not the association should be validated as part of 
def validate?
  !options[:validate].nil? ? options[:validate] : (options[:autosave] == true || collection?)
end