swift - 从使用 CoreData 创建的 mapView 中删除图钉

Question

我有一个带有自定义注释的 map View 。注释是从 coreData 加载的。我希望用户能够单击注释来编辑或删除引脚。 我真的很难尝试仅删除选定的注释。我是编程新手，甚至是核心数据新手，所以请原谅我的无知。 这是我试图实现的功能。使用此功能不会删除或打印任何内容。

func  deletePin() {
    let appDelegate = UIApplication.shared.delegate as! AppDelegate
    let context = appDelegate.persistentContainer.viewContext
    let requestDel = NSFetchRequest<NSFetchRequestResult>(entityName: "Fish")

    let thisCatch = selectedAnnotation?.title
    requestDel.returnsObjectsAsFaults = false

    let predicateDel = NSPredicate(format: "species == %d", thisCatch!)
    requestDel.predicate = predicateDel


    do {
        let locations = try context.fetch(requestDel)
        for location in locations{
            context.delete(location as! NSManagedObject)

            self.map.removeAnnotation(selectedAnnotation!)
            print("pinDeleted")
        }
    } catch {
        print("Failed")
    }

    do {
        try context.save()
    } catch {
        print("Failed saving")
    }
}

这是我尝试调用deletePin()的扩展

extension MapViewController: ExampleCalloutViewDelegate {
func mapView(_ mapView: MKMapView, didTapDetailsButton button: UIButton, for annotation: MKAnnotation) {



    let alert = UIAlertController(title: "Edit or Delete", message: "Any changes are permenate!", preferredStyle: .alert)
    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)

    let deleteDataAction = UIAlertAction(title: "delete", style: .destructive, handler: { action in

        self.deletePin()

       // self.map.removeAnnotation(annotation)
      //  print(annotation.title!)

Answer 1

我在扩展中使用此代码使其正常工作。

extension MapViewController: ExampleCalloutViewDelegate {
func mapView(_ mapView: MKMapView, didTapDetailsButton button: UIButton, for annotation: MKAnnotation) {



    let alert = UIAlertController(title: "Edit or Delete", message: "Any changes are permenate!", preferredStyle: .alert)
    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)

    let deleteDataAction = UIAlertAction(title: "delete", style: .destructive, handler: { action in

        let pinTitle = self.selectedAnnotation?.title

            do{
                let request: NSFetchRequest<Fish> = Fish.fetchRequest()
                let predicate = NSPredicate(format: "species == %@", pinTitle!)
                request.predicate = predicate

                let locations = try self.context.fetch(request)
                for location in locations{
                    self.context.delete(location)

                    self.map.removeAnnotation(self.selectedAnnotation!)
                    print("pinDeleted")
                }
            } catch {
                print("Failed")
        }

        do {
            try self.context.save()
        } catch {
            print("Failed saving")
        }

    })

就我而言，selectedAnnotation.title 是时间和日期，因此它是唯一的 ID 如果有人有更简洁的设置方法，请告诉我!