引用在 AppDelegate 中创建的 NSPersistentStore 实例 [英] Referring to NSPersistentStore instances created in AppDelegate
问题描述
我修改了您通过核心数据应用程序获得的样板核心数据堆栈代码,将两个 NSPersistentStore
添加到 NSPersistentStoreCoordinator
而不是一个.
I modified the boilerplate core data stack code you get with a core data application to add two NSPersistentStore
s to the NSPersistentStoreCoordinator
instead of just one.
// MARK: - Core Data stack
lazy var applicationDocumentsDirectory: NSURL = {
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as NSURL
}()
lazy var managedObjectModel: NSManagedObjectModel = {
let modelURL = NSBundle.mainBundle().URLForResource("DB", withExtension: "momd")!
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
var error: NSError? = nil
let firstStoreURL = self.applicationDocumentsDirectory.URLByAppendingPathComponent("first-store.sqlite")
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: firstStoreURL, options: nil, error: &error) == nil {
coordinator = nil
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
let secondStoreURL = self.applicationDocumentsDirectory.URLByAppendingPathComponent("second-store.sqlite")
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: secondStoreURL, options: nil, error: &error) == nil {
coordinator = nil
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
return coordinator
}()
lazy var managedObjectContext: NSManagedObjectContext? = {
let coordinator = self.persistentStoreCoordinator
if coordinator == nil {
return nil
}
var managedObjectContext = NSManagedObjectContext()
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
// MARK: - Core Data Saving support
func saveContext() {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
}
我需要在添加 NSManagedObject
对象时指定存储,如下所示.
I need to specify the store when adding NSManagedObject
objects like below.
let someObject = NSManagedObject(entity: "someEntity", insertIntoManagedObjectContext: context)
context.assignObject(someObject, toPersistentStore: <store instance>)
并指定我需要从中获取数据的商店.
And specifying the stores which I need to fetch data from like this.
let entityDescription = NSEntityDescription.entityForName("someEntity", inManagedObjectContext: context)
let fetchRequest = NSFetchRequest()
fetchRequest.entity = entityDescription
fetchRequest.affectedStores = [<store instance>]
我的问题是如何获得对在 AppDelegate 中创建的那些 NSPersistentStore
的引用?
My question is how can I get a reference to those NSPersistentStore
s created in the AppDelegate?
为了清楚起见,我已经知道如何获得对 AppDelegate 本身的引用.
Just to be clear, I already know how to get a reference to the AppDelegate itself.
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
获取 NSPersistentStore
部分是我卡住的地方.
It's the getting the NSPersistentStore
part is where I'm stuck.
我尝试像这样在 AppDelegat 中将它创建为一个单独的属性,但我不知道如何从 persistentStoreCoordinator
调用它/添加它.
I tried creating it as a separate property in the AppDelegat like this but I don't know how to call it/add it from persistentStoreCoordinator
.
var firstStore: NSPersistentStore {
var store: NSPersistentStore!
if let coordinator = persistentStoreCoordinator {
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("first-store.sqlite")
var error: NSError?
store = coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error)!
}
return store
}
除了每当我调用这个属性时,它不会向协调器添加一个商店的新实例吗?
Besides whenever I call this property, wouldn't it add a new instance of a store to the coordinator?
推荐答案
有一个 persistentStores
property 在 NSPersistentStoreCoordinator
上,您可以为此使用目的.它返回一个(大概)NSPersistentStore
实例的数组.
There is a persistentStores
property on NSPersistentStoreCoordinator
you can use for this purpose. It returns an array of (presumably) NSPersistentStore
instances.
// Get the first store, assuming it exists
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
let firstStore = appDelegate.persistentStoreCoordinator.persistentStores[0] as NSPersistentStore
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