当 persistContainer 不在 swift 的 App delegate 方法中时，如何从核心数据中删除所有数据

Question

我是 Swift 新手，我想删除核心数据中的所有数据。我见过几个例子，但在所有例子中persistentContainer都是 in AppDelegate，而在我的例子中persistentContainer则不是AppDelegate。它属于不同的类，如下所示：

class CoreDataStack: NSObject {
    
    static let sharedInstance = CoreDataStack()
    private override init() {}
    
    func applicationDocumentsDirectory() {
        if let url = FileManager.default.urls(for: .libraryDirectory, in: .userDomainMask).last {
            print(url.absoluteString)
        }
    }
    lazy var persistentContainer: NSPersistentContainer = {
       
        let container = NSPersistentContainer(name: "Database")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
            print(storeDescription)
            
        })
        return container
    }()
    
    // MARK: - Core Data Saving support
    
    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}

在 AppDelegate 方法中，我只是将其称为

CoreDataStack.sharedInstance.applicationDocumentsDirectory()

func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
        CoreDataStack.sharedInstance.saveContext()
    }

我尝试了这段代码，但它对我不起作用。

Answer 1

解决方案之一可以是用于NSBatchDeleteRequest持久容器中的所有实体。您可以将这些方法添加到您的CoreDataStack：

func deleteAllEntities() {
    let entities = persistentContainer.managedObjectModel.entities
    for entity in entities {
        delete(entityName: entity.name!)
    }
}

func delete(entityName: String) {
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
    do {
        try persistentContainer.viewContext.execute(deleteRequest)
    } catch let error as NSError {
        debugPrint(error)
    }
}

完整代码可以在这里找到