NSManagedObject临时使用，如何在NSObject和NSManagedObject之间切换

Question

Im using a Core Data model for my iPhone app. I have been looking for a way to instantiate or use an Entity outside the ManagedObjectContext. (This should not be done, I know, Im also more looking for a way to not do that, but get the benefits anyway).

My challenge is that I have a view where the user can search for "Persons", all the search results are parsed and put into a Person managedObject then displayed in a list. If the user clicks a Person from the list, then and only then would I like the Person entity to be persisted to the store, however this requires me to delete all the other results so they don't get persisted along with the desired one. Also to the best of my knowledge, if the user decides to quite the app, the store is persisted, potentially with all current search results mixed in with real user data!

Is there some way I could have a TempPerson NSObject I could use for the search list? Without, however, me having to manually pull the 45 attributes from the temp object and manually set them on the managedObject!

Sort of like: NSManagedObject aPersonCorrectlyReturnedFromTheStore = (NSManagedObject *)tempPersonOfJustTypeNSObject

I have seen example code from Apple where they build a temporary store to facilitate undo/redo and other stuff on an object that is not yet persisted. This I feel would be overkill in my situation. I just need to display search results until the user selects a Person to persist.

Hope it is clear what Im trying to do, feeling like my Core Data vocabulary isn't quite large enough yet:)

Thanks for any suggestions.

Answer 1

You could create each temporary person object as an NSDictionary or NSMutableDictionary. You can then create a new Person managed object and use the fact that NSManagedObject instances are KVC compliant and use setValuesForKeysWithDictionary:.

Answer 2

New managed objects that are inserted are not actually persisted until you send the managed object context a save: message.
Keep track of them in a collection (set or array) -- you are probably already doing this since you are presenting the search results somehow. Then, delete ( deleteObject: ) them all except for the one(s) that the user selects.
The deleted managed objects will never be stored.