如何在swift中将数据完全存储在核心数据中后才调用数据抓取函数？

import CoreData

class DataManager {
    static let shared = DataManager()
    private init() {}
    
    lazy var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: "YourModelName")
        container.loadPersistentStores { (storeDescription, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        }
        return container
    }()
    
    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
                fetchData()
            } catch {
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
    
    func fetchData() {
        // 实现数据抓取逻辑
        print("Fetching data after save...")
    }
}

// 使用示例
let dataManager = DataManager.shared
// 假设你已经有了一个NSManagedObject实例
let managedObject = ... // 初始化你的NSManagedObject
dataManager.persistentContainer.viewContext.insert(managedObject)
dataManager.saveContext()