ios - 获取错误: "Cannot convert value of type ' NSFetchRequest<NSManagedObject >' to expected argument type ' NSFetchRequest<NSFetchRequestResults >'"

Question

使用此函数对表格 View 中的单元格进行排序。我的获取请求中出现错误。 do 循环内的行 notes = try context.fetch(request) 导致错误，请求带有下划线

错误显示“无法将类型“NSFetchRequest”的值转换为预期参数类型“NSFetchRequest””

我的TableViewController文件

 import UIKit
import CoreData
 

class noteTableViewController: UITableViewController {
 
    var notes = [Note]()

    var managedObjectContext: NSManagedObjectContext? {
 
        return (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
 
    }
 

    func loadDataFromDatabase() {
 
        let settings = UserDefaults.standard

        let sortPriority = settings.string(forKey: Constants.kPriority)

        let context = appDelegate.persistentContainer.viewContext

        let request = NSFetchRequest<NSManagedObject>(entityName: "Note")

        let sortDescriptor = NSSortDescriptor(key: sortPriority)

        let sortDescriptorsArray = [sortDescriptor]

        request.sortDescriptors = sortDescriptorsArray

        do {
 
            notes = try context.fetch(request)
        } catch let errer as NSError {
 
            print("Could not fetch. \(error), \(error.userInfo)")
        }

 
    }

 
}

Answer 1

试试这个:

func loadDataFromDatabase() {
  ...

  let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Note")

  ...

  do {
    notes = try context.fetch(request) as? [Note] ?? []
  } catch let errer as NSError {
    print("Could not fetch. \(error), \(error.userInfo)")
  }
}

当然，我假设您的 Note 类是 NSManagerObject 的子类。