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我正在关注来自Ray Wenderlich团队的过时tutorial，该团队使用命令行工具应用程序遍历了应用Core Data-backed应用程序的重新填充。如何使用核心数据模型与内存中的存储类型使用预填充的SQLite文件？
我已成功预先填充预定实体，并通过执行NSFetchRequest进行验证。
现在，我想在我的单元测试中使用相同的预填充数据来验证我与CoreData的交互正确发生。我试图设置我的模拟CoreDataStack子类使用内存中的存储，但是当我试图验证我有我的单元测试中使用的预填充数据时，我得到0的count。
类负责与我的应用程序的目标CoreData互动，名为CoreDataStack，如下：
/// The object that is responsible for managing interactions with Core Data.
internal class CoreDataStack {
// MARK: - Properties
/// The name of the `NSManagedObjectModel` object used for storing information with Core Data.
private let modelName: String
/// The `NSManagedObjectContext` object that is associated with the main queue.
internal lazy var mainContext: NSManagedObjectContext = {
return self.storeContainer.viewContext
}()
/// The `NSPersistentContainer` object that encapsulates the application's Core Data stack.
internal lazy var storeContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: self.modelName)
let directory = NSPersistentContainer.defaultDirectoryURL()
let storeURL = directory.appendingPathComponent("\(self.modelName).sqlite")
if !FileManager.default.fileExists(atPath: (storeURL.path)) {
guard let populatedURL = Bundle.main.url(forResource: self.modelName, withExtension: "sqlite") else {
fatalError("Invalid populated .sqlite file URL")
}
do {
try FileManager.default.copyItem(at: populatedURL, to: storeURL)
} catch {
fatalError("Error: \(error)")
}
}
let description = NSPersistentStoreDescription()
description.url = storeURL
container.persistentStoreDescriptions = [description]
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Error: \(error)")
}
})
return container
}()
// MARK: - Initialization
/// Returns an instance of `CoreDataStack`.
/// - parameter modelName: The name of the `NSManagedObjectModel` object used for storing information with Core Data.
internal init(modelName: String) {
self.modelName = modelName
}
/// Attempts to save items to Core Data by committing changes to `NSManagedObject`s in a `NSManagedObjectContext`.
/// - parameter context: The `NSManagedObjectContext` of which changes should be committed.
internal func saveContext(_ context: NSManagedObjectContext) {
context.perform {
do {
try context.save()
} catch let error as NSError {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
}
}
}
的CoreDataStack，MockCoreDataStack的子类，用于测试如下：
internal class MockCoreDataStack: CoreDataStack {
// MARK: - Initialization
convenience init() {
self.init(modelName: "Currency")
}
override init(modelName: String) {
super.init(modelName: modelName)
let container = NSPersistentContainer(name: modelName)
let directory = NSPersistentContainer.defaultDirectoryURL()
let storeURL = directory.appendingPathComponent("\(modelName).sqlite")
if !FileManager.default.fileExists(atPath: (storeURL.path)) {
guard let populatedURL = Bundle(for: type(of: self)).url(forResource: modelName, withExtension: "sqlite") else {
fatalError("Invalid populated .sqlite file URL")
}
do {
try FileManager.default.copyItem(at: populatedURL, to: storeURL)
} catch {
fatalError("Error: \(error)")
}
}
let description = NSPersistentStoreDescription()
description.url = storeURL
description.type = NSInMemoryStoreType
container.persistentStoreDescriptions = [description]
container.loadPersistentStores { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
}
self.storeContainer = container
}
}
产生的count我的提取请求的单元测试目标是0。我希望返回包含预填充对象数量的count，就像我在返回应用程序目标中的count时所得到的一样。
我做了什么不正确的事情导致我没有返回预期的结果？