Swift-在Cocoa中使用核心數據

Question

我正在為OS X應用程序使用Core Data 。 語言是Swift 。 它對Cocoa的作用方式有些奇怪。 以下是Xcode創建的內容的簡短版本。

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
            }
        }
    }()
}

在向實體添加新記錄后，找不到用於核心數據的SQLite文件。 上面的代碼中沒有指向SQLite文件的指針。 以下是iOS對應版本。

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
    }()
}

上面的代碼指向一個SQLite文件。 因此，我可以輕松地將記錄插入實體。

我正在使用Xcode 7.2.1我在做錯什么嗎？ 還是這是Xcode錯誤？

Answer 1

您在此處發布的代碼只是功能性Core Data堆棧的一部分，不足以初始化Core Data。

這是Apple當前用於初始化Core Data Stack的示例代碼：

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)")
            }
        }
    }
}

請參閱從Apple 初始化Core Data Stack 。

Answer 2

@DuncanBabbage解決方案的Swift 3版本：

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)")
            }
        }
    }
}