多线程核心数据 - persistentStoreCoordinator 与 parentContext

Question

我正在尝试解决因从多个线程访问同一个 NSManagedObjectContext 而导致的问题。我在 Apple docs 中找到以下内容：

let moc = … //Our primary context on the main queue

let privateMOC = NSManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)
privateMOC.parentContext = moc

privateMOC.performBlock {
    //...
}

这似乎是我所追求的。我还在 tutorial 中发现了一些非常相似的东西，它已更新为 iOS 9:

let privateContext = NSManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)
privateContext.persistentStoreCoordinator = coreDataStack.context.persistentStoreCoordinator

privateContext.performBlock { () -> Void in
  //...
}

他们似乎都达到了相同的目的，但是 Apple 文档的版本使用 parentContext 而不是直接使用 persistantStoreCoordinator。这两种方法有什么区别？

Answer 1

使用parentContext。自 iOS 5.

以来，这优于使用持久存储协调器的方法

Prior to OS X v10.7 and iOS v5.0, the parent store is always a persistent store coordinator. In OS X v10.7 and later and iOS v5.0 and later, the parent store may be another managed object context. Ultimately the root of a context’s ancestry must be a persistent store coordinator. The coordinator provides the managed object model and dispatches requests to the various persistent stores containing the data.

在您的具体情况下：

If a context’s parent store is another managed object context, fetch and save operations are mediated by the parent context instead of a coordinator. This pattern has a number of usage scenarios, including:

Performing background operations on a second thread or queue.

来源：NSManagedObjectContext class 参考，“Parent Store”。

多线程核心数据 - persistentStoreCoordinator 与 parentContext

Multithreaded Core Data - persistentStoreCoordinator vs parentContext

multithreading

core-data

nsmanagedobjectcontext

ios

swift