Swift 4 in Xcode 9 - 读取核心数据中的数据失败

Question

我的函数read()有一个谓词不能正常工作，我设置了“no”0可以读取所有数据，如果我设置其他则不能。

class DataClass
{
    private(set) var no: Int16?
    private(set) var title: String?
    private(set) var content: NSAttributedString?

    init(no: Int16,
         title: String,
         content: NSAttributedString)
    {
        self.no = no
        self.title = title
        self.content = content
    }
}


func read(no: Int16) -> DataClass?
    {
        let ReadData = DataClass()

        let appDelegate:AppDelegate = UIApplication.shared.delegate as! AppDelegate
        let managedObjectContext = appDelegate.persistentContainer.viewContext

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

        let request = NSFetchRequest<Note>(entityName: "Note")
        request.fetchOffset = 0
        request.entity = entity

        print("noBtnDn: \(no)")
        let predicate = NSPredicate(format: "no == %@", NSNumber(value: no))
        request.predicate = predicate

        do{
            let results = try managedObjectContext.fetch(request)
            print("results`count: \(results.count)")
            for note in results
            {
                //ReadData.title = note.title!
                //ReadData.content = (note.content as? NSAttributedString)!
                ReadData.ReadFromNote(note: note)
                print("no: \(note.no)")
            }
        }
        catch{
            print("Failed to read data.")
            return nil
        }
        return ReadData

    }

它打印 resultscount: 24* when no=0 (the count of all data is 24),print *results count: 0 当 no!=0 时。数据的“no”没有0，都是从1开始的

所以当 no=0 时，打印

noBtnDn: 0
results` count: 24
no: 1
no: 2
no: 3
...
no: 24

不知道为什么找不到正确的“no”，是不是我的功能用错了？

Answer 1

您的 class 是否符合核心数据属性？

您是否也尝试过将可选的 Int16 变为非可选的？

Swift 4 in Xcode 9 - 读取核心数据中的数据失败

Swift 4 in Xcode 9 - Read data in core data failed

xcode

ios

swift

swift4

xcode9