ios - NSBatchUpdateRequest 在 Swift 中引发错误

Question

这是我的NSBatchUpdateRequest:

    let batchUpdateRequest = NSBatchUpdateRequest(entityName: "WLItem")
    batchUpdateRequest.predicate = NSPredicate(format: "source != rt")
    batchUpdateRequest.propertiesToUpdate = ["position": 2]
    batchUpdateRequest.resultType = NSBatchUpdateRequestResultType.UpdatedObjectsCountResultType

    do {
        let batchUpdateResult = try NSManagedObjectContext.MR_defaultContext().executeRequest(batchUpdateRequest) as! NSBatchUpdateResult
    } catch {
        print("error: \(error)")
    }

控制台输出为:

error: NilError

怎么了？ XCode7有问题吗？我是第一次使用 NSBatchUpdateRequest，所以我不知道以前是不是这样。对我来说，该代码应该可以正常工作。

Answer 1

您必须刷新 managedContextObject 才能更新数据库。我创建了一个函数，其中使用 NSBatchUpdateRequest 更新数据库。下面是函数:-

 let managedContext = SharedInstance.appDelegate?.persistentContainer.viewContext


func updateDataFromTable(tableName:String, idOfPaticularTable ID:String, updatedDict:Dictionary<String, String>, success:@escaping (_ response:Bool)-> Void, failure:@escaping (_ error: Error?) -> Void) {

    let batchRequest = NSBatchUpdateRequest(entityName: tableName)
    let predicate = NSPredicate(format: "id == %@", ID)

    batchRequest.predicate = predicate
    batchRequest.propertiesToUpdate = updatedDict

    batchRequest.resultType = .updatedObjectIDsResultType
    do {
        // Execute Batch Request
        let batchUpdateResult = try managedContext?.execute(batchRequest) as! NSBatchUpdateResult

        // Extract Object IDs
        let objectIDs = batchUpdateResult.result as! [NSManagedObjectID]

        for objectID in objectIDs {
            // Turn Managed Objects into Faults
            let managedObject = managedContext?.object(with: objectID)
            managedContext?.refresh(managedObject!, mergeChanges: false)
        }
        success(true)
    } catch let error as NSError {
        print(error)
        failure(error)
    }
}

struct SharedInstance {

   static let appDelegate = UIApplication.shared.delegate as? AppDelegate

   static let employeetable = "EmployeeModel"
}