swift - 核心数据在不同线程中获取和保存

Question

我创建了一个 Coredatacontroller 类来处理所有核心数据操作。该类中编写了一种获取当前上下文的方法。

func getCurrentContext() -> NSManagedObjectContext {
        var curMOC:NSManagedObjectContext? = self.managedObjectContext
        let thisThread:Thread = Thread.current
        print("This thread: ", thisThread)
        if thisThread == Thread.main {
            if curMOC != nil {
                return curMOC!
            }
            let coordinator:NSPersistentStoreCoordinator? = self.persistentStoreCoordinator
            if coordinator != nil {
                curMOC = NSManagedObjectContext(concurrencyType: NSManagedObjectContextConcurrencyType.mainQueueConcurrencyType)
                curMOC?.persistentStoreCoordinator = coordinator
            }
            return curMOC!
        }
        // if this is some other thread....
        // Get the current context from the same thread..
        var threadManagedObjectContext:NSManagedObjectContext? = thisThread.threadDictionary.object(forKey:"MOC_KEY") as? NSManagedObjectContext;
        // Return separate MOC for each new thread
        if threadManagedObjectContext != nil {
            return threadManagedObjectContext!;
        }

        let coordinator:NSPersistentStoreCoordinator? = self.persistentStoreCoordinator
        if coordinator != nil {
            threadManagedObjectContext = NSManagedObjectContext(concurrencyType: NSManagedObjectContextConcurrencyType.privateQueueConcurrencyType)
            threadManagedObjectContext?.persistentStoreCoordinator = coordinator
            threadManagedObjectContext?.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
            thisThread.threadDictionary.setObject(threadManagedObjectContext!, forKey: "MOC_KEY" as NSCopying)
        }
        return threadManagedObjectContext!;
    }

我正在使用 NSOperation 子类上传一些图像，因此对于每个图像都会创建一个 NSOperation 对象。在 NSOperation 的完成 block 内，我从 CoreData 获取一些数据并更新它。

问题:提取不会返回核心数据中存在的记录如果在获取方法中我使用 mainmanagementobjectcontext，那么我会获取记录，但是当我使用 currentcontext 保存它时，它不会反射(reflect)对核心数据的更改。我也在 NSOperation 子类中编写了通知观察者方法，但该方法从未被调用。请建议应该做什么!!

Answer 1

处理来自不同线程的 CoreData 对象非常复杂。我建议使用CoreStore ，它将为您完成所有上下文处理。

设置示例:

let dataStack: DataStack = {
    let dataStack = DataStack(xcodeModelName: "ModelName")
    do {
        try dataStack.addStorageAndWait()
    } catch let error {
        print("Cannot set up database storage: \(error)")
    }
    return dataStack
}()

对象创建示例:

func addUser(id: String, name: String) {
    dataStack.perform(asynchronous: { transaction in
        let user = transaction.create(Into<User>())
        user.id = id
        user.name = name
    }, completion: { _ in })
}

对象获取示例:

func printUserName(id: String) {
    dataStack.perform(asynchronous: { transaction in
        guard let user = transaction.fetchOne(From<User>(), Where("id", isEqualTo: id) else {
            return
        }
        print(user.name)
    }, completion: { _ in })
}