Swift - 将核心数据与 Cocoa 一起使用

Question

我正在为 OS X 应用程序使用Core Data。语言是Swift。 Cocoa 的工作方式有些奇怪。以下是 Xcode 创建的较短版本。

class AppDelegate: NSObject, NSApplicationDelegate {
    func applicationDidFinishLaunching(aNotification: NSNotification) {
        // Insert code here to initialize your application
    }

    func applicationWillTerminate(aNotification: NSNotification) {
        // Insert code here to tear down your application
    }

    // MARK: - Core Data stack
    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. (The directory for the store is created, if necessary.) This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
        let fileManager = NSFileManager.defaultManager()
        var failError: NSError? = nil
        var shouldFail = false
        var failureReason = "There was an error creating or loading the application's saved data."

        // Make sure the application files directory is there
        do {
            let properties = try self.applicationDocumentsDirectory.resourceValuesForKeys([NSURLIsDirectoryKey])
            if !properties[NSURLIsDirectoryKey]!.boolValue {
                failureReason = "Expected a folder to store application data, found a file \(self.applicationDocumentsDirectory.path)."
                shouldFail = true
            }
        } catch  {
            let nserror = error as NSError
            if nserror.code == NSFileReadNoSuchFileError {
                do {
                    try fileManager.createDirectoryAtPath(self.applicationDocumentsDirectory.path!, withIntermediateDirectories: true, attributes: nil)
                } catch {
                    failError = nserror
                }
            } else {
                failError = nserror
            }
        }
    }()
}

在我向实体添加新记录后，找不到 Core Data 的 SQLite 文件。上面的代码中没有指向 SQLite 文件的指针。以下是iOS对应。

class AppDelegate: UIResponder, UIApplicationDelegate {
    // MARK: - Core Data stack
    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.URLByAppendingPathComponent("SingleViewCoreData.sqlite")
        var failureReason = "There was an error creating or loading the application's saved data."
        do {
            try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
        } catch {
            // Report any error we got.
            var dict = [String: AnyObject]()
            dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
            dict[NSLocalizedFailureReasonErrorKey] = failureReason

            dict[NSUnderlyingErrorKey] = error as NSError
            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()
        }

        return coordinator
    }()
}

上面的代码指向一个 SQLite 文件。所以我在向实体插入记录时没有问题。

我正在使用 Xcode 7.2.1 我做错了吗？或者这是一个 Xcode 错误？

Answer 1

Swift 3 版本的@DuncanBabbage 解决方案：

class DataController: NSObject {
    var managedObjectContext: NSManagedObjectContext
    override init() {
        // This resource is the same name as your xcdatamodeld contained in your project.
        guard let modelURL = Bundle.main.url(forResource: "DataModel", withExtension:"momd") else {
            fatalError("Error loading model from bundle")
        }
        // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
        guard let mom = NSManagedObjectModel(contentsOf: modelURL) else {
            fatalError("Error initializing mom from: \(modelURL)")
        }
        let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)
        managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = psc

        DispatchQueue.global(qos: DispatchQoS.QoSClass.background).async {
            let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
            let docURL = urls[urls.endIndex-1]
            /* The directory the application uses to store the Core Data store file.
             This code uses a file named "DataModel.sqlite" in the application's documents directory.
             */
            let storeURL = docURL.appendingPathComponent("DataModel.sqlite")
            do {
                try psc.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: storeURL, options: nil)
            } catch {
                fatalError("Error migrating store: \(error)")
            }
        }
    }
}

Answer 2

您在此处发布的代码只是功能核心数据堆栈的一部分，不足以初始化核心数据。

这是 Apple 当前用于初始化核心数据堆栈的示例代码：

import CoreData
class DataController: NSObject {
    var managedObjectContext: NSManagedObjectContext
    init() {
        // This resource is the same name as your xcdatamodeld contained in your project.
        guard let modelURL = NSBundle.mainBundle().URLForResource("DataModel", withExtension:"momd") else {
            fatalError("Error loading model from bundle")
        }
        // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
        guard let mom = NSManagedObjectModel(contentsOfURL: modelURL) else {
            fatalError("Error initializing mom from: \(modelURL)")
        }
        let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)
        managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = psc
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0)) {
            let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
            let docURL = urls[urls.endIndex-1]
            /* The directory the application uses to store the Core Data store file.
             This code uses a file named "DataModel.sqlite" in the application's documents directory.
             */
            let storeURL = docURL.URLByAppendingPathComponent("DataModel.sqlite")
            do {
                try psc.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil)
            } catch {
                fatalError("Error migrating store: \(error)")
            }
        }
    }
}

请参阅 Apple 的 Initialising the Core Data Stack。