ios - 如何在 swift 3 中添加带有 ConcerrencyType 的 NSManagedObjectContext？

Question

在我的应用程序中，我有下载数据并将它们保存到 CoreData 的任务。在我迁移到 swift 3 之后，它开始在随机时间保存数据时抛出异常。据我了解，如果我对所有操作使用一个上下文，就会发生这种情况。现在我创建了另一个具有并发类型的上下文，一切正常，但没有任何内容保存到 .sqlite 文件:)这是我创建上下文的方法:

static let context : NSManagedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
static let privateContext = NSManagedObjectContext(concurrencyType: NSManagedObjectContextConcurrencyType.privateQueueConcurrencyType)

static func declare()
{
    AixmParser.privateContext.parent = AixmParser.context
}

我这样保存数据:

    do{
        try privateContext.save()
    }
    catch{
    }

我是否必须向声明或核心数据堆栈添加一些内容？

更新:下面的核心数据堆栈。

// MARK: - Core Data stack

lazy var persistentContainer: NSPersistentContainer = {
    /*
     The persistent container for the application. This implementation
     creates and returns a container, having loaded the store for the
     application to it. This property is optional since there are legitimate
     error conditions that could cause the creation of the store to fail.
    */
    let container = NSPersistentContainer(name: "AppName")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

            /*
             Typical reasons for an error here include:
             * The parent directory does not exist, cannot be created, or disallows writing.
             * The persistent store is not accessible, due to permissions or data protection when the device is locked.
             * The device is out of space.
             * The store could not be migrated to the current model version.
             Check the error message to determine what the actual problem was.
             */
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
        container.viewContext.perform({
            // actions upon the NSMainQueueConcurrencyType NSManagedObjectContext for this container
        })

    })
    return container
}()

// MARK: - Core Data Saving support

func saveContext () {
    let context = persistentContainer.viewContext
    if context.hasChanges {
        do {
            try context.save()
        } catch {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            let nserror = error as NSError
            fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
        }
    }
}

Answer 1

首先，您必须创建从 privateContext 到 NSPercientContainer 的 viewContext 的链接。所以，在创建私有(private)的同时， privateContext，privateContext.parentContext = viewContext。保存时 让上下文 = privateContext
而(上下文!=无){
上下文.save()
上下文 = context.privateContext
这会起作用。我不确定你为什么一开始就收到错误。