从appDelegate中的SQL文件进行Swift 3预加载 [英] Swift 3 preload from SQL files in appDelegate

问题描述

我正在尝试快速3转换.我正在swift 2项目中从sql文件中预加载数据.我不确定如何使它在Swift 3.0中工作吗?以下是我的swift 2 appDelegate文件.在swift 3中，核心数据堆栈已发生足够的变化，以至于我不知道在哪里尝试重用与swift 2相同的代码.我正在使用的代码在注释为SQLite预加载添加"下列出. .谢谢

I am attempting a swift 3 conversion. I was preloading data from sql files in my swift 2 project. I am unsure how to make this work in swift 3.0? Below is my swift 2 appDelegate file. In swift 3 the core data stack has changed enough, that I do not know where to try to reuse the same code that worked for me with swift 2. The code i was using that worked is listed under the comment "added for SQLite preload". Thank you

    // MARK: - Core Data stack

lazy var applicationDocumentsDirectory: URL = {
    // The directory the application uses to store the Core Data store file. This code uses a directory named "self.edu.SomeJunk" in the application's documents Application Support directory.
    let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    return urls[urls.count-1]
}()

lazy var managedObjectModel: NSManagedObjectModel = {
    // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
    let modelURL = Bundle.main.url(forResource: "ESLdata", withExtension: "momd")!
    return NSManagedObjectModel(contentsOf: modelURL)!
}()

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("ESLdata.sqlite")



    //ADDED FOR SQLITE PRELOAD
    // Load the existing database
    if !FileManager.default.fileExists(atPath: url.path) {
        let sourceSqliteURLs = [Bundle.main.url(forResource: "ESLdata", withExtension: "sqlite")!,Bundle.main.url(forResource: "ESLdata", withExtension: "sqlite-wal")!, Bundle.main.url(forResource: "ESLdata", withExtension: "sqlite-shm")!]
        let destSqliteURLs = [self.applicationDocumentsDirectory.appendingPathComponent("ESLdata.sqlite"), self.applicationDocumentsDirectory.appendingPathComponent("ESLdata.sqlite-wal"), self.applicationDocumentsDirectory.appendingPathComponent("ESLdata.sqlite-shm")]
        for index in 0 ..< sourceSqliteURLs.count {
            do {
                try FileManager.default.copyItem(at: sourceSqliteURLs[index], to: destSqliteURLs[index])
            } catch {
                print(error)
            }
        }
    }
    // END OF ADDED CODE



    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:  [NSMigratePersistentStoresAutomaticallyOption:true, NSInferMappingModelAutomaticallyOption:true])
    } catch {
        // 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 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
}()

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
}()

// MARK: - Core Data Saving support

func saveContext () {
    if managedObjectContext.hasChanges {
        do {
            try managedObjectContext.save()
            print("SAVED")
        } catch {
            print("Save Failed")

            let nserror = error as NSError
            NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
            abort()
        }
    }
}

以下是我尝试将代码更新到的内容，但没有运气:

The following is what I attempted to update the code to, and had no luck:

func getDocumentsDirectory()-> URL {
    let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    let documentsDirectory = paths[0]
    return documentsDirectory
}

// MARK: - Core Data stack

lazy var persistentContainer: NSPersistentContainer = {
    /*
     The persistent container for the application. This implementation
     creates and returns a container, having loaded 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.
     */





    let container = NSPersistentContainer(name: "ESLdata")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() 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.

            /*
             Typical reasons for an error here include:
             * The parent directory does not exist, cannot be created, or disallows writing.
             * The persistent store is not accessible, due to permissions or data protection when the device is locked.
             * The device is out of space.
             * The store could not be migrated to the current model version.
             Check the error message to determine what the actual problem was.
             */
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
        //ADDED FOR SQLITE PRELOAD

        let url = self.getDocumentsDirectory().appendingPathComponent("ESLdata.sqlite")
        // Load the existing database

        if !FileManager.default.fileExists(atPath: url.path) {
            let sourceSqliteURLs = [Bundle.main.url(forResource: "ESLdata", withExtension: "sqlite")!,Bundle.main.url(forResource: "ESLdata", withExtension: "sqlite-wal")!, Bundle.main.url(forResource: "ESLdata", withExtension: "sqlite-shm")!]
            let destSqliteURLs = [self.getDocumentsDirectory().appendingPathComponent("ESLdata.sqlite"), self.getDocumentsDirectory().appendingPathComponent("ESLdata.sqlite-wal"), self.getDocumentsDirectory().appendingPathComponent("ESLdata.sqlite-shm")]
            for index in 0 ..< sourceSqliteURLs.count {
                do {
                    try FileManager.default.copyItem(at: sourceSqliteURLs[index], to: destSqliteURLs[index])
                } catch {
                    print(error)
                }
            }
        }
        // END OF ADDED CODE


    })
    return container
}()

// MARK: - Core Data Saving support

func saveContext () {
    let context = persistentContainer.viewContext
    if context.hasChanges {
        do {
            try context.save()
        } catch {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() 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.
            let nserror = error as NSError
            fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
        }
    }
}

推荐答案

首先-您所做的更改仅部分涉及Swift3.您不需要使用NSPersistentContainer，而这样做完全是与使用Swift 3的问题不同.您仍然可以使用与Swift 2中相同的所有Core Data类和方法，但是语法不同.如果您了解较旧的代码，则最好保留相同的逻辑和类，但使用较新的语法.

First of all-- the changes you have made are only partly about Swift 3. You are not required to use NSPersistentContainer, and doing so is a completely different issue from using Swift 3. You can still use all the same Core Data classes and methods as in Swift 2, but with different syntax. If you understand your older code, you're probably better off keeping the same logic and classes but with newer syntax.

如果执行切换到NSPersistentContainer，则loadPersistentStores方法或多或少可与您的旧代码中的addPersistentStore调用相提并论.调用该方法时，将加载持久性存储文件，因此如果要使用其数据，该文件必须存在.在较旧的代码中，您在加载持久性存储之前复制了预加载的数据，但是在较新的代码中，您随后进行了此操作.这就是为什么您看不到数据的原因.

If you do switch to NSPersistentContainer, the loadPersistentStores method is more or less comparable to the addPersistentStore call in your older code. When you call that method, the persistent store file is loaded, so it must exist if you want to use its data. In your older code you copy your pre-loaded data before loading the persistent store, but in your newer code you're doing it afterward. That's why you're not seeing the data.

由于您似乎使用的是与NSPersistentContainer相同的默认存​​储文件名，这可能就足够了.如果仍然找不到数据，则可能需要创建NSPersistentStoreDescription来告诉容器将存储文件放置在何处.

Since you appear to be using the same default store file name that NSPersistentContainer will assume, that's probably enough. If it still doesn't find the data, you may need to create an NSPersistentStoreDescription to tell your container where to put the store file.

但是，如果您是我，我会坚持使用较旧的方法和较新的Swift 3语法.

But if I were you I'd stick with the older approach and the newer Swift 3 syntax.

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