ios - 无法访问核心数据

Question

我正在开发一个运行应用程序，由于某种原因，当我尝试访问数据以将其映射出来时，出现错误sudo gem install cocoapods-deintegrate cocoapods-clean

fatal error :在解包可选值时意外发现 nil

和

线程 1:EXC_BAD_INSTRUCTION(代码=EXC_I386_INVOP，子代码=0x0)位于以下行

let locations = run.locations

如果我把它改成

let locations = run?.locations

我在应用程序中收到“else{”消息，但它没有崩溃。

我知道数据在那里，因为我与 Liya 确认过。不知道为什么我的应用程序看不到它。

这是其余的代码

    var run : Run!

    func loadMap() {
    guard
        let locations = run.locations,
        locations.count > 0,
        let region = mapRegion()
        else {
            let alert = UIAlertController(title: "Error",
                                          message: "Sorry, this run has no locations saved",
                                          preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "OK", style: .cancel))
            present(alert, animated: true)
            return
    }
    print("loadMap")
    mapView.setRegion(region, animated: true)

    mapView.add(polyLine())
}

TIA

Answer 1

布埃诺!谢谢。

好的。所以就在这里

已删除

    var run : Run!

声明一个空数组，因为获取返回 [Any]

    var locations : [Any] = [] 

添加委托(delegate)

let appDelegate = UIApplication.shared.delegate as? AppDelegate

然后将获取数据函数编写为带有完成处理程序的扩展

extension MapsViewController {
func fetch(completion: (_ complete: Bool) -> ()) {
    guard let managedContext = appDelegate?.persistentContainer.viewContext else { return }

    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Location")

    do{
        locations = try managedContext.fetch(fetchRequest) //Trys to call CoreData and returns an Array of type [Any] and assigns them to the array of locations
        print("fetched data")
        completion(true)

    } catch {
        debugPrint("could not fetch: \(error.localizedDescription)")
        completion(false)
    }
}