Question

当我启动我的应用程序时，我从服务器下载了几张照片，然后将其保存到coreData（我遵循了本教程：Saving Picked Image to CoreData）

extension NewsFeedViewController {



    func getContext() {
        saveQueue.sync {


        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        self.managedContext = appDelegate.persistentContainer.viewContext
        }
    }
}

extension NewsFeedViewController {

    func prepareImageForSaving(image:UIImage) {

        // use date as unique id
        let date : Double = NSDate().timeIntervalSince1970

        // dispatch with gcd.
        convertQueue.async() {
            print("dd")
            // create NSData from UIImage
            guard let imageData = UIImageJPEGRepresentation(image, 1) else {
                // handle failed conversion
                print("jpg error")
                return
            }


            // scale image, I chose the size of the VC because it is easy


            // send to save function
            self.saveImage(imageData: imageData as NSData, date: date)

        }
    }
}

extension NewsFeedViewController {

    func saveImage(imageData:NSData, date: Double) {


        saveQueue.async(flags: .barrier) {

            // create new objects in moc
            guard let moc = self.managedContext else {

                return
            }

            guard let fullRes = NSEntityDescription.insertNewObject(forEntityName: "Blogger", into: moc) as? FullRes else {
                // handle failed new object in moc
                print("moc error")
                return
            }

            //set image data of fullres
            fullRes.imageData = imageData as Data


            // save the new objects
            do {

                 try moc.save()

            } catch {
                fatalError("Failure to save context: \(error)")
            }

            // clear the moc
            moc.refreshAllObjects()
        }

    }

}


extension NewsFeedViewController {

    func loadImages(_ fetched:@escaping (_ images:[FullRes]?) -> Void) {

        saveQueue.async() {
            guard let moc = self.managedContext else {
                return
            }

            let fetchRequest :NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "FullRes")
            //let fetchRequest = NSFetchRequest(entityName: "FullRes")//NSFetchRequest(entityName: "FullRes")
            print(fetchRequest)

            do {

                let results = try moc.fetch(fetchRequest)
                let imageData = results as? [FullRes]
                DispatchQueue.main.async() {
                    fetched(imageData)

                }
            } catch let error as NSError {
                print("Could not fetch \(error), \(error.userInfo)")
                return
            }
        }
    }

}

在该代码中我正在准备要保存的图像 - 保存它，然后在我的代码的其他部分（未在此处发布）并检查是否存在互联网连接。如果没有加载图像，那么我调用上面发布的loadImages（）函数。

调用它时出现此错误：

如果有人可以帮助我，我们非常感谢!!

Answer 1

我将let fetchRequest更改为此

let fetchRequest: NSFetchRequest<NSFetchRequestResult> = FullRes.fetchRequest()

Answer 2

您的代码没有问题。我已经实现了您的确切代码，它运行良好。您现在应该尝试隔离您的问题。尝试评论使用互联网的功能，例如处理登录用户的功能和下载内容。

同时检查AppDelegate，查看在没有互联网的情况下启动App时可能导致早期崩溃的功能。

始终尝试捕获由于缺少可访问性而导致的异常。

为此我正在使用以下功能：

import Foundation
import SystemConfiguration

open class Reachability {

    class func isConnectedToNetwork() -> Bool {

        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(MemoryLayout.size(ofValue: zeroAddress))
        zeroAddress.sin_family = sa_family_t(AF_INET)

        guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress , {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {zeroSockAddress in
                SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
            }
        }) else {
            return false
        }

        var flags : SCNetworkReachabilityFlags = []
        if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
            return false
        }

        let isReachable = flags.contains(.reachable)
        let needsConnection = flags.contains(.connectionRequired)
        return (isReachable && !needsConnection)
    }

}

被叫：

if Reachability.isConnectedToNetwork() == true {
    //execute your code
} else {
    //catch print
}

从coreData加载图像时崩溃

2 个答案: