CODEWITHSUNDEEP
iosswiftcore-datansmanagedobjectnsmanagedobjectcontext
martin
martin

Reputation: 1974

Retrieving a managed objects ID with NSURL

I'm trying to retrieve and create a managed object from a NSURL saved in my user-defaults, but I can't figure out how to use the managedObjectIDForURIRepresentation-function. My code looks like this:

func setCoreData(){
    let defaults = NSUserDefaults.standardUserDefaults()
    let usedKeyName = "timerList"
    let usedList = defaults.objectForKey(usedKeyName) as? [NSURL] ?? []
    let url:NSURL = usedList[0] as NSURL

    let managedobject:NSManagedObjectID = //What do I write here?

}

Any suggestions would be appreciated.

Upvotes: 2

Views: 1902

Answers (1)

quellish
quellish

Reputation: 21254

To obtain an NSManagedObjectID from the URI representation, you must call the appropriate method on the NSManagedObjectContext or NSPersistentStoreCoordinator - managedObjectIDForURIRepresentation:.

The URI representation includes the UUID of the store used to persist the object. Calling managedObjectIDForURIRepresentation: will cause Core Data to attempt to find the correct store based on that information, and then use the rest of the URI to locate that specific object. Because of this make sure your store's UUID is not changing every time you start up. If Core Data cannot find the data associated with the URI representation managedObjectIDForURIRepresentation: will return nil.

So, for instance, you would do something like:

NSManagedObjectID objectId = [[managedObjectContext persistentStoreCoordinator] managedObjectIDForURIRepresentation:uri];

Or in swift:

let objectId:NSManagedObjectID = persistentStoreCoordinator.managedObjectIDForURIRepresentation(uri)

Upvotes: 8

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