如何将字符串保存到CoreData数组的开头

let entity = NSEntityDescription.entity(forEntityName: "YourEntityName", in: managedObjectContext)

let newObject = NSManagedObject(entity: entity!, insertInto: managedObjectContext)
newObject.setValue(yourString, forKey: "yourStringAttribute")

let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "YourEntityName")
let sortDescriptor = NSSortDescriptor(key: "yourStringAttribute", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]

do {
    let results = try managedObjectContext.fetch(fetchRequest) as! [NSManagedObject]
    // results 数组中包含了已存在的实体对象
} catch {
    print("Fetch failed: \(error)")
}

results.insert(newObject, at: 0)

do {
    try managedObjectContext.save()
} catch {
    print("Save failed: \(error)")
}