也许有人有使用大型核心数据库的经验(我的基础中有 32k 行,我需要向用户展示所有这些基础并在其中进行一些搜索),当我尝试读取基础时到我的 fetchedResultsController 我有 3-5 秒的延迟,我该如何解决这个问题?我可以在一些后台线程中阅读这个基础吗?或者如果我通过关系在某些部分上分开我的基础是否有帮助?我尝试在 viewDidAppear 中加载我的基地
override func viewDidAppear(_ animated: Bool) {
DispatchQueue.main.async {
self.connectFetchedRequest()
self.tableView.reloadData()
self.indicatorLoad.stopAnimating()
}
}
func connectFetchedRequest() {
do {
try self.fetchedResultsController.performFetch()
}catch {
print(error)
}
}
对于在基中搜索,我使用 UISearchBarDelegate 方法(但在向 searchText 添加字符时我仍然有一些“滞后”)
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
block?.cancel()
block = DispatchWorkItem {
let predicate = NSPredicate(format: "cardName contains[c] %@", searchText)
self.fetchedResultsController.fetchRequest.predicate = predicate
self.connectFetchedRequest()
DispatchQueue.main.async(execute: {
self.tableView.reloadData()
})
}
DispatchQueue.global(qos: .background).asyncAfter(deadline: .now() + 0.5, execute: block!)
}
我使用以下代码创建了 fetchedResultsController
lazy var context: NSManagedObjectContext = {
let appDelegate = (UIApplication.shared.delegate as? AppDelegate)
return appDelegate!.managedObjectContext
}()
lazy var fetchedResultsController: NSFetchedResultsController<CardsBaseClass> = {
let fetchRequest = NSFetchRequest<CardsBaseClass>(entityName: "CardsBase")
let sortDescriptor = NSSortDescriptor(key: "cardName", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
fetchRequest.fetchBatchSize = 50
fetchRequest.returnsObjectsAsFaults = false
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.context, sectionNameKeyPath: nil, cacheName: nil)
fetchedResultsController.delegate = self
return fetchedResultsController
}()
为了从其他 viewController 添加新的谓词(我打开 .overFullScreen 所以我的主视图与 base 也是打开的)我使用以下代码
predicateArrayClass.addPredicate(predicate: predicateType)
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "updateTableViewByNewPredicate"), object: nil, userInfo: nil)
self.dismiss(animated: true, completion: nil)
我在哪里调用了更新 fetchResultController func
func updateTableViewByNewPredicate() {
searchController.searchBar.text! = ""
let predicateArray = predicateArrayClass.arrayOfPredicates
block = DispatchWorkItem {
self.fetchedResultsController.fetchRequest.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: predicateArray)
self.connectFetchedRequest()
DispatchQueue.main.async(execute: {
self.tableView.reloadData()
})
}
DispatchQueue.global(qos: .background).async(execute: block!)
}