Question

当我在iOS 9中使用Xcode 7.3时代码运行良好但是当我使用swift 3迁移到Xcode 8时，下面的代码向我显示运行时错误。仍然找到解决方案

class TableViewController: UITableViewController,NSFetchedResultsControllerDelegate,UISearchResultsUpdating {
    var fetchResultController :NSFetchedResultsController<Restaurant>!
    var searchController : UISearchController!
    var searchResults :[Restaurant]  = []

    override func viewDidLoad() {
        super.viewDidLoad()

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

        if let managedObjectContext = (UIApplication.shared.delegate as? AppDelegate)?.managedObjectContext{
            fetchResultController = NSFetchedResultsController(fetchRequest: fetchRequest as! NSFetchRequest<Restaurant>, managedObjectContext: managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)

            fetchResultController.delegate = self

            do{
                try fetchResultController.performFetch()
                restaurants = fetchResultController.fetchedObjects!
            }
            catch{
                print(error)
            }

        }
    }
}

Answer 1

从下面的代码我可以看到，你得到一个餐馆对象

var fetchResultController :NSFetchedResultsController<Restaurant>!
var searchController : UISearchController!
var searchResults :[Restaurant]  = []

但是在你的fetchRequest中，你将它定义为NSFetchRequestResult。

let fetchRequest : NSFetchRequest<NSFetchRequestResult>  = Restaurant.fetchRequest()

它可能是一个NSFetchRequestResult，但我建议你直接把它当作餐馆。我有一个类似的问题，这样做有效。试试这个，看看它是否有效。

let fetchRequest : NSFetchRequest<Restaurant>  = Restaurant.fetchRequest()

Answer 2

试试这个：

<强> - ＆GT;转到应用代理

在 last 卷曲括号后输入：

let ad = UIApplication.shared.delegate as! AppDelegate
let context = ad.persistenceContainer.viewContext

<强> - ＆GT;返回TableViewController

删除if let。

<强>类型：

var fetchResultController = NSFetchResultsController(
  fetchRequest: Your fetchRequest, 
  manageObjectContext: context (From the delegate), 
  sectionNameKeyPath: nil, cacheName: nil
)
self.fetchResultController = fetchResultController

NSFetchedResultsController的一个实例需要iOS 10中的非零fetchRequest和managedObject Context

2 个答案: