在核心数据更改处理期间捕获到异常，尝试使用 userInfo (null) 插入 nil

Question

我在我的应用程序中使用 coreData 来保存多个表（大约 30 个），它工作正常但随机崩溃，出现以下异常：

    [error] error: Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  -[__NSCFSet addObject:]: attempt to insert nil with userInfo (null)
CoreData: error: Serious application error. 
 Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  -[__NSCFSet addObject:]: attempt to insert nil with userInfo (null)
2017-06-16 15:05:56.043490+0500 Sales CRM[619:85792]
 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFSet addObject:]: attempt to insert nil'
 *** First throw call stack:
(0x1872c6fe0 0x185d28538 0x1872c6f28 0x1871e316c 0x1895c2028 0x1895c1218 0x1895c97d0 0x1895c019c 0x1001d6888 0x1001bb78c 0x1000a43d8 0x1878d034c 0x1878e8048 0x187d95814 0x187cda770 0x187ccab28 0x187d97bb0 0x100f85a10 0x100f932e8 0x100f89634 0x100f95630 0x100f9539c 0x186387100 0x186386cac)
libc++abi.dylib: terminating with uncaught exception of type NSException

我搜索了很多，但大多数解决方案都在 Objective C 中，甚至我也遵循了一些解决方案，但没有一个有效。

这是我的代码：

 public class ServiceCalls : NSManagedObject {
  /*
    class func getContext () -> NSManagedObjectContext {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate

        let moc = NSManagedObjectContext(concurrencyType:.mainQueueConcurrencyType)
        let privateMOC = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
        privateMOC.parent = moc

        privateMOC.perform({
            do {
                try privateMOC.save()
            } catch {
                fatalError("Failure to save context: \(error)")
            }
        })
        return appDelegate.persistentContainer.viewContext
    }
   */ // tried this but didn't work as well

     class func getContext () -> NSManagedObjectContext {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        return appDelegate.persistentContainer.viewContext
    }

上面是我的上下文，每次我从任何数据库保存或获取任何东西时都会调用它。以下是我在 coreData 中的保存方式：

let context = getContext()
    let entity =  NSEntityDescription.entity(forEntityName: "DoctorsDetail_Tbl", in: context)
    let newDoc = NSManagedObject(entity: entity!, insertInto: context)

    newDoc.setValue(empid, forKey: "empId")
    newDoc.setValue(doctorid, forKey: "docId")



    //save the object
    do {
        try context.save()
        print("saved Doctors in Database yayy!")

    } catch let error as NSError  {
        print("Could not save \(error), \(error.userInfo)")
    } catch {
        let nserror = error as NSError
        fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
    }
}

Answer 1

有时您会在数据源 (empid, doctorid) 中获得 nil 值，您希望将其插入到 coredata 中

在您想向数据库插入值之前检查nil。

func test()  {
    for (key, value) in self {
        if let unwrappedValue = value.asOptional {
            print("Unwrapped value for '\(key)' is '\(unwrappedValue)'")
        } else {
            print("Value for '\(key)' is nil")
        }
    }
}

用途：

var dict: [String: AnyObject?] = [
    "key1" : "value1",
    "key2": nil,             // your program is unexpectedly crashing here 
    "key3": "somevalue"
]

dict.test()   // calling test fuction

---

过滤数组中的 nil：

extension Array {
    static func filterNils(array: [T?]) -> [T] {
        return array.filter { $0 != nil }.map { $0! }
    }
}

用途：

var array:[Int?] = [1, nil, 2, 3, nil]

Array.filterNils(array)

希望这会有所帮助。