在数据模型或NSManagedObject的自定义子类中定义的瞬态属性之间有区别吗?

I was reading that setting the value of a transient property always results in marking the managed object as "dirty". However, what I don't get is this: If I make a subclass of NSManagedObject and use some extra properties which I don't need to be persistet, how does Core Data know about them and how can it mark the object as dirty when I access these? I was reading that setting the value of a trans