我正在尝试执行以下操作：
点击UITableView单元格的单元格，然后segue到下一个UIViewController并显示数据库结果。但是有多个持久存储，因此指定的存储由单元格标签文本指定。
问题是：如何使用该方法persistentStore(for: url)？或者有没有其他方法可以为fetchRequest指定持久存储？
这是我的代码不起作用：
func wordFetchRequest() -> NSFetchRequest<Word> {
let fr = NSFetchRequest<Word>(entityName: "Word")
fr.fetchBatchSize = 100
// Assigning sort descriptors
let firstLetterSort = NSSortDescriptor(key: #keyPath(Word.firstLetter), ascending: true)
let spellSort = NSSortDescriptor(key: #keyPath(Word.spell), ascending: true)
fr.sortDescriptors = [firstLetterSort, spellSort]
// Get URL of the designated store to fetch
let libname = (AppDelegate.nameDict as NSDictionary).allKeys(for: nameToFetch).first!
// I'm not sure the following line: which file should I use? I've tried
//.sqlite, .sqlite-shm and .sqlite-wal but none worked.
let url = AppDelegate.coreDataStack.storeDirectory.appendingPathComponent("(libname).sqlite-wal")
// Specify affected store for the fetch request
var pss = [NSPersistentStore]()
print(url)
// The following line fails:
if let ps = coreDataStack.psc.persistentStore(for: url) {
pss.append(ps)
} else {
}
fr.affectedStores = pss
print(fr.affectedStores ?? "No stores available.")
return fr
}
任何帮助将不胜感激。
我不得不处理类似的情况，其中我有不同的持久存储(具体类型为NSInMemoryStoreType类型之一，NSSQLiteStoreType
类型为特定类型) 我发现为每个存储创建单独的持久存储协调器并使用这些持久存储创建单独的托管对象上下文更容易，因为父存储:)
这是用iOS 9 swift 3编写的代码，因此具有较旧的核心数据堆栈操作，我看过iOS 10 Swift 3 Core数据堆栈，我相信这些方法仍然可以让您了解这里所说的内容:)
这是您将在Coredata堆栈中默认看到的内容，getterforpersistentStoreCoordinator
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
// The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
// Create the coordinator and store
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.appendingPathComponent("SingleViewCoreData.sqlite")
var failureReason = "There was an error creating or loading the application's saved data."
do {
try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
log.debug(url)
} catch let error as NSError {
// Report any error we got.
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject?
dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject?
dict[NSUnderlyingErrorKey] = error
let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error (wrappedError), (wrappedError.userInfo)")
abort()
}
catch{
}
return coordinator
}()
这里的重要声明是
try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
如您所见，它将持久存储类型指定为 Sqlite，并将 configurationName 指定为 nil，这意味着默认配置:)
您可以在 Coredata 中创建多个配置，并在此语句中指定名称，以便为每个配置创建单独的持久存储协调器:)
你可以看看我的博客 核心数据能否与敏感信息信任，了解如何创建多个配置和存储:)
因此，假设您创建了另一个配置并向它们添加了实体，并将其称为"Test1"配置，您将为此创建一个单独的持久存储协调器，
lazy var test1PersistentStoreCoordinator: NSPersistentStoreCoordinator = {
// The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
// Create the coordinator and store
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.appendingPathComponent("SingleViewCoreData.sqlite")
var failureReason = "There was an error creating or loading the application's saved data."
do {
try coordinator.addPersistentStore(ofType: NSInMemoryStoreType, configurationName: "Test1", at: url, options: nil)
log.debug(url)
} catch let error as NSError {
// Report any error we got.
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject?
dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject?
dict[NSUnderlyingErrorKey] = error
let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error (wrappedError), (wrappedError.userInfo)")
abort()
}
catch{
}
return coordinator
}()
现在，您有两个与两个不同配置关联的持久存储协调器，只需使用这些持久存储协调器作为其父存储:)创建两个托管对象上下文
lazy var managedObjectContext: NSManagedObjectContext = {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
lazy var managedObjectContextForBackTracking : NSManagedObjectContext = {
let coordinator = self.test1PersistentStoreCoordinator
var managedObjectContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
就是这样:)
现在，在相应的托管对象上下文上运行提取请求:)并确保没有任何内容弄乱您的核心数据:)
希望对:)有所帮助