Swift：executeFetchRequest：无法转换'Any Object'类型的值

Question

I have some problem about executeFetchRequest

import UIKit
import CoreData

class BeaconDB: NSObject {

    var addStatus: BeaconAddStatus!


    enum BeaconAddStatus{
          case DUPLICATE_IN_AD
          case ADDED_SUCCESSFULL
          case ERROR_IN_ADD
     }


    func addNewBeacon(beacon: BeaconData) -> BeaconAddStatus{
          print("ADDNewBeacon")
          print("uuid: %@ \(beacon.uuid)")

    let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let context: NSManagedObjectContext = appDelegate.managedObjectContext

    let entityDesc: NSEntityDescription = NSEntityDescription.entityForName("Beacon", inManagedObjectContext: context)!
    let request: NSFetchRequest = NSFetchRequest()
    let predSearch: NSPredicate = NSPredicate(format: "(uuid = %@) AND (major = %@) AND (minor = %@) \(beacon.uuid), \(beacon.major), \(beacon.minor)")

    request.entity = entityDesc
    request.predicate = predSearch

    do {
        let existingBeacon: Beacons = try context.executeFetchRequest(request)
        // success ...
    } catch let error as NSError {
        // failure
        print("Fetch failed: \(error.localizedDescription)")
    }

}

}

Mv Beacons class is NSManagedObject

  import UIKit

  import CoreData

  class Beacons: NSManagedObject {

      dynamic var major : NSNumber = 0.0
      dynamic var minor : NSNumber = 0.0
      dynamic var name : NSString = ""
      dynamic var uuid : NSString = ""
   }

But it's error from this line

 let existingBeacon: Beacons = try context.executeFetchRequest(request)

Cannot convert value of type ['Any Object'] to specified type 'Beacons'

Help me please Thank you :))

Answer 1

Two issues:

• executeFetchRequest returns always an array of objects.
• You have to cast the type.

---

let existingBeacons = try context.executeFetchRequest(request) as! [Beacons]

Cannot convert value of type ... to specified type ... means usually the compiler needs help by casting the type or there is no relation at all.

PS: It's recommended to name Core Data entities in the singular form to avoid confusion.