swift - CoreData合并变更

Question

在我的旧项目中，我设置了核心数据存储和模型。在此模型中，我使用 NotificationCenter 来观察 NSManagedObjectContext。每当保存一个上下文时，它就会与其他上下文合并:

NotificationCenter.default.addObserver(self, selector: #selector(didSaveContext), name: .NSManagedObjectContextDidSave, object: nil)

@objc func didSaveContext(notification: Notification) {
    guard let sender = notification.object as? NSManagedObjectContext else { return }

    if sender === mainContext {
        userContext.perform { self.userContext.mergeChanges(fromContextDidSave: notification) }
        idleContext.perform { self.idleContext.mergeChanges(fromContextDidSave: notification) }
    } else if sender === userContext {
        mainContext.perform { self.mainContext.mergeChanges(fromContextDidSave: notification) }
        idleContext.perform { self.idleContext.mergeChanges(fromContextDidSave: notification) }
    } else if sender === idleContext {
        mainContext.perform { self.idleContext.mergeChanges(fromContextDidSave: notification) }
        userContext.perform { self.idleContext.mergeChanges(fromContextDidSave: notification) }
    } else {
        userContext.perform { self.userContext.mergeChanges(fromContextDidSave: notification) }
        mainContext.perform { self.mainContext.mergeChanges(fromContextDidSave: notification) }
        idleContext.perform { self.idleContext.mergeChanges(fromContextDidSave: notification) }
    }
}

但是从 iOS10 开始，Apple 引入了 NSPersistentContainer，我可以使用:

persistentContainer.viewContext.automaticallyMergesChangesFromParent = true

这是否意味着我不必再使用通知中心来合并更改？

Answer 1

Does this mean I don't have to use the notification center to merge the changes anymore?

不，您必须实现通知并调用 mergeChanges() 来合并更改。