引用在AppDelegate中创建的NSPersistentStore实例 | 引用在AppDelegate中创建的NSPersistentSt

本文介绍了引用在AppDelegate中创建的NSPersistentStore实例的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我修改了核心数据应用程序获得的样板核心数据栈代码，将 NSPersistentStore 添加到 NSPersistentStoreCoordinator

  // MARK： - 核心数据堆栈
 lazy var applicationDocumentsDirectory：NSURL = { 
 let urls = NSFileManager.defaultManager（）。URLsForDirectory（.DocumentDirectory，inDomains：.UserDomainMask）
返回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）
如果coordinator !.addPersistentStoreWithType（NSSQLiteStoreType，configuration：nil，URL：firstStoreURL，options：nil ，错误：&错误）== nil {
 coordinator = nil 
 NSLog（未解析的错误\（错误），\（错误！.userInfo））
 abort 
} 
 
 let secondStoreURL = self.applicationDocumentsDirectory.URLByAppendingPathComponent（second-store.sqlite）
如果coordinator！.addPersistentStoreWithType（NSSQLiteStoreType，configuration：nil，URL：secondStoreURL，选项：nil，错误：&错误）== nil {
 coordinator = nil 
 NSLog（未解决的错误\（错误），\（错误！.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： - 核心数据保存支持
 func saveContext（）{
如果let moc = self .managedObjectContext {
 var error：NSError？ = nil 
如果moc.hasChanges&& ！moc.save（& error）{
 NSLog（未解决的错误\（错误），\（错误！.userInfo））
 abort（）
} $ b b} 
}

我需要在添加 NSManagedObject 下面的对象。

  let someObject = NSManagedObject（entity：someEntity，insertIntoManagedObjectContext：context ）
 context.assignObject（someObject，toPersistentStore：< store instance>）

  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 NSPersistentStore 的引用？
 
 
 为了清楚起见，我已经知道如何获取对AppDelegate本身的引用。
  let appDelegate = UIApplication.sharedApplication（）。委托为AppDelegate 
  
  NSPersistentStore 部分是我被困的地方。
 
 
 
 
 
 尝试创建它作为一个单独的属性在AppDelegat像这样，但我不知道如何调用它/从 persistentStoreCoordinator 添加
  var firstStore：NSPersistentStore {
 var store：NSPersistentStore！ 
如果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 
} 
  
属性，不会向协调器添加一个存储的新实例？ 
解决方案
有一个 persistentStores  在 NSPersistentStoreCoordinator 您可以使用为此目的。它返回一个（可能） NSPersistentStore 实例的数组。
 获取第一个商店，假设它存在
 let appDelegate = UIApplication.sharedApplication（）。委托为AppDelegate 
让firstStore = appDelegate.persistentStoreCoordinator.persistentStores [0]作为NSPersistentStore 
  
 
I modified the boilerplate core data stack code you get with a core data application to add two NSPersistentStores 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()
        }
    }
}
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>)
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>]
My question is how can I get a reference to those NSPersistentStores created in the AppDelegate?
Just to be clear, I already know how to get a reference to the AppDelegate itself.
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
It's the getting the NSPersistentStore part is where I'm stuck.
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
}
Besides whenever I call this property, wouldn't it add a new instance of a store to the coordinator? 
 解决方案 
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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