在 Swift 3 中实现 fetchedresultsviewcontroller

Posted 2023-03-04

【中文标题】在 Swift 3 中实现 fetchedresultsviewcontroller

【英文标题】：Implementing fetchedresultsviewcontroller in Swift 3

【发布时间】：2017-02-27 18:09:18

【问题描述】：

我正在尝试，在将控制器的委托属性设置为 self 时遇到以下错误：

无法将类型“SomeRootViewController”的值分配给类型 'NSFetchedResultsControllerDelegate?'

SomeRootViewController.swift

@available(ios 10.0, *)
@objc class SomeRootViewController: UIViewController, UITableViewDataSource, UITableViewDelegate 

    var delegate: SomeRootViewControllerDelegate?
    public var context: NSManagedObjectContext!

    private let persistentContainer = NSPersistentContainer(name: "Accessory")


    fileprivate lazy var fetchedResultsController: NSFetchedResultsController<Accessory> = 
        // Create Fetch Request
        let fetchRequest: NSFetchRequest<Accessory> = Accessory.fetchRequest() as! NSFetchRequest<Accessory>

        // Configure Fetch Request
        fetchRequest.sortDescriptors = [NSSortDescriptor(key: "AccessoryAttributes.name", ascending: true)]

        // Create Fetched Results Controller
        let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)

        // Configure Fetched Results Controller
        fetchedResultsController.delegate = self //<<-- this is where error occurs

        return fetchedResultsController
    ()

有人可以向我解释一下这个问题以及如何解决它吗？

【参考方案1】：

因为您将委托设置为 self，您还需要使 SomeRootViewController 符合 NSFetchedResultsControllerDelegate 协议，如下所示：

class SomeRootViewController: NSFetchedResultsControllerDelegate, UIViewController, UITableViewDataSource, UITableViewDelegate