core data firing fault

摘自：pro core data for ios

Core Data uses the term firing faults when it must pull the data from the persistent store that a fault points to and then put it into memory. Core Data has ‘‘fired’’ off a request to fetch data from the data store, and the fault has been ‘‘fired’’ from its job to represent the actual data. You cause a fault to fire any time you request a managed object’s persistent data, whether through valueForKey: or through methods of a custom class that either return or access the object’s persistent data. Methods that access a managed object’s metadata and not any of the data stored in the persistent store don’t fire a fault. This means you can query a managed object’s class, hash, description, entity, and object ID, among other things, and not cause a fault to fire.