Illegal attempt to establish a relationship problem.

"in different contexts" means that the two managed objects have been created in different NSManagedObjectContext instances.

If you created a managed object context in the new view controller, you need to get a new NSManagedObject instance for the object:

let objectID = managedObject.objectID

let copy = context2.objectWithID(objectID)

See:

developer.apple.com/library/etc/redirect/xcode/ios/1151/documentation/Cocoa/Conceptual/CoreData/FrequentlyAskedQuestions.html

"How do I copy a managed object from one context to another?"

The best approach I've ever found is to use dedicated Queue for all database operations:

class Queues {

    private struct queues {
        static var dbQueue: dispatch_queue_t!
        static var dispatchToken: dispatch_once_t = 0
    }

    class var dbQueue: dispatch_queue_t {
        get {
            dispatch_once(&queues.dispatchToken, { () -> Void in
                queues.dbQueue = dispatch_queue_create("db_queue", nil)
            })
            return queues.dbQueue
        }
    }
}

and then in your Persistence.swift:

class func DoSomething() {
     dispatch_async(Queues.dbQueue, { () -> Void in
          ...
     })
}

if you need to send result back use the following:

class func DoSomething(closure:(SomeType)->()) {
     dispatch_async(Queue.dbQueue, { () -> Void in
          ...
               dispatch_async(dispatch_get_main_queue(), { () -> Void in
                      closure(result)
               })
     })
}

In this way you will never need to synchronize context objects because the access to the NSManagedObject objects happens is single context.

class Persistence {
   
    class var context : NSManagedObjectContext {
        let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
        return appDelegate.managedObjectContext!
    }
     ...
}

Thanks a lot. You solved my problem.

When pass ManagedObject from last viewcontroller , it need to retrive it from managedContext(backgroundContext)

let objectID = schedule.objectID

let belongSchedule = self.cdh.backgroundContext?.objectWithID(objectID) as! Schedule

newDailyPlan.schedule = belongSchedule // schedule is relationship

self.cdh.saveContext(self.cdh.backgroundContext!)