segueing时出现核心数据错误:无法在NSManagedObject类上调用指定的初始值设定项
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我有一个视图控制器,当点击mapView上的一个引脚时,它会转到另一个视图控制器。 “Pin”是一个NSManagedObject,它在被发送到第二个视图控制器之前会被填充纬度和经度(其中一个函数用实际图像填充它)。
在我的didSelect函数完成之后和调用performSegue函数之前,我收到错误“CoreData:error:无法在NSManagedObject类'Pin'上调用指定的初始值设定项”。
@nonobjc public class func fetchRequest() -> NSFetchRequest<Pin> {
return NSFetchRequest<Pin>(entityName: "Pin")
}
@NSManaged public var latitude: Double
@NSManaged public var longitude: Double
@NSManaged public var images: NSSet?
这是班级:
convenience init(latitude: Double, longitude: Double, context: NSManagedObjectContext) {
if let entity = NSEntityDescription.entity(forEntityName: "Pin", in: context) {
self.init(entity: entity, insertInto: context)
self.latitude = latitude
self.longitude = longitude
} else {
fatalError("Unable to find entity name")
}
}
我已经尝试将引脚声明为可选,并强制用“!”声明它。这两个选项都不起作用。根据我在线学习和阅读的内容,我需要使用指定的初始化程序初始化pin变量。这是我在视图控制器类顶部的尝试,但它也不起作用。
var pin = Pin.init(entity: NSEntityDescription.entity(forEntityName: "Pin", in: CoreDataStack.sharedInstance().context)!, insertInto: CoreDataStack.sharedInstance().context)
创建引脚:
// Create the annotation
let touchPoint = gestureRecognizer.location(in: mapView)
let newCoordinate = self.mapView.convert(touchPoint, toCoordinateFrom:self.mapView)
let annotation = MKPointAnnotation()
annotation.coordinate = newCoordinate
pin = Pin(latitude: annotation.coordinate.latitude, longitude: annotation.coordinate.longitude, context: CoreDataStack.sharedInstance().context)
let pinAnnotation = PinAnnotation(objectID: pin.objectID, title: nil, subtitle: nil, coordinate: annotation.coordinate)
// Add the annotation
mapView.addAnnotation(pinAnnotation)
CoreDataStack.sharedInstance().saveContext()
在didSelect中选择引脚:
do {
let pinAnnotation = view.annotation as! PinAnnotation
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Pin")
let predicate = NSPredicate(format: "latitude == %@ AND longitude == %@", argumentArray: [pinAnnotation.coordinate.latitude, pinAnnotation.coordinate.longitude])
fetchRequest.predicate = predicate
let pins = try CoreDataStack.sharedInstance().context.fetch(fetchRequest) as? [Pin]
pin = pins![0]
} catch let error as NSError {
print("failed to get pin by object id")
print(error.localizedDescription)
return
}
self.performSegue(withIdentifier: "collectionViewSegue", sender: self)
......并执行segue:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "collectionViewSegue" {
let controller = segue.destination as! CollectionViewController
print("CoreDataStack context in segue= (CoreDataStack.sharedInstance().context)")
controller.selectedPin = pin
if let images = pin.images?.allObjects as? [Images] {
controller.photos = images
}
print("PrepareForSegue pin properties are:
latitude: (pin.latitude)
longitude: (pin.longitude)")
}
}
我错过了什么?
答案
我通过在我的类的开头使变量声明可选来解决这个问题:
var selectedPin: Pin?
...并在我的长按gestureRecognizer功能中进行不同的初始化:
@objc func handleLongPress(_ gestureRecognizer : UIGestureRecognizer) {
if gestureRecognizer.state != .began { return }
print("Tap gesture recognized")
// Create the annotation
let touchPoint = gestureRecognizer.location(in: mapView)
let newCoordinate = self.mapView.convert(touchPoint, toCoordinateFrom:self.mapView)
let annotation = MKPointAnnotation()
annotation.coordinate = newCoordinate
// Initialize NSManagedObject 'Pin' with properties
selectedPin = Pin(context: CoreDataStack.sharedInstance().context)
selectedPin?.latitude = annotation.coordinate.latitude
selectedPin?.longitude = annotation.coordinate.longitude
if let selectedPin = selectedPin {
let pinAnnotation = PinAnnotation(objectID: selectedPin.objectID, title: nil, subtitle: nil, coordinate: annotation.coordinate)
// Add the annotation
mapView.addAnnotation(pinAnnotation)
}
CoreDataStack.sharedInstance().saveContext()
print("This is what the ole save looks like: (CoreDataStack.sharedInstance().context)")
}
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