CoreData 更新后不保存信息

Posted 2023-05-07

【中文标题】CoreData 更新后不保存信息

【英文标题】：CoreData not saving information after being updated

【发布时间】：2015-07-29 15:47:13

【问题描述】：

这个函数应该将当前日期添加到一个列表中，只要按下 addButton 就存储在内存中，但是当应用程序关闭并重新加载时，新日期不会出现。切换视图后数据似乎也消失了。

var selectedPersonFirst = ""
var selectedPersonLast = ""
let today = NSDate()



let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext

@IBAction func addButtonPressed(sender: AnyObject) 

    let entityDescription = NSEntityDescription.entityForName("People", inManagedObjectContext: managedObjectContext!)
    let request = NSFetchRequest()
    request.entity = entityDescription

    let firstPred = NSPredicate(format: "(firstName = %@)", selectedPersonFirst)
    let secondPred = NSPredicate(format: "(lastName = %@)", selectedPersonLast)

    let predicate = NSCompoundPredicate(type: NSCompoundPredicateType.OrPredicateType, subpredicates: [firstPred, secondPred])
    request.predicate = predicate

    var error: NSError?

    var objects = managedObjectContext?.executeFetchRequest(request, error: &error)

    if let results = objects

        let days = results[0].valueForKey("days") as! NSMutableArray
        days.addObject(NSDate())

        let person = results[0] as! People
        person.setValue(days, forKey: "days")

    

    managedObjectContext!.save(nil)

    self.tableView.reloadData()

这是 NSManagedObject 的 people 子类：

import Foundation
import CoreData

class People: NSManagedObject 

    @NSManaged var days: AnyObject
    @NSManaged var dayZero: NSDate
    @NSManaged var firstName: String
    @NSManaged var gender: String
    @NSManaged var lastName: String

在其中创建days NSMutableArray 的 ViewController：

import UIKit
import CoreData

class NewPersonViewController: UIViewController 

    @IBOutlet weak var firstName: UITextField!
    @IBOutlet weak var lastName: UITextField!
    @IBOutlet weak var gender: UISegmentedControl!
    @IBOutlet weak var dayZeroDate: UIDatePicker!

    let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext

    var personName : String = ""
    var currentDayNumber : Int? = nil

    override func viewDidLoad() 
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    

    override func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    




    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) 
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.

        if segue.identifier == "DoneNewPersonSegue" 

            let entityDescription = NSEntityDescription.entityForName("People", inManagedObjectContext: managedObjectContext!)

            let person = People(entity: entityDescription!, insertIntoManagedObjectContext: managedObjectContext)

            person.firstName = self.firstName.text
            person.lastName = self.lastName.text
            person.days = NSMutableArray()
            person.gender = gender.description
            person.dayZero = dayZeroDate.date

            save()

        



    

    func save() 
        var error : NSError?
        if(managedObjectContext!.save(&error) ) 
            println(error?.localizedDescription)
        
    

数据模型：

【问题讨论】：

如何在您的数据模型中声明days？您在哪里创建用于它的初始 NSMutableArray？

@TomHarrington days 在实体People 中声明为Transformable 类型的属性。最初的 NSMutableArray 是另一个视图类，我将更新问题以包含代码

你确定 objects 不是 nil（即 fetch 没有抛出错误）吗？另外，如果它不是 nil，它可能包含几个对象？我注意到你的谓词使用.OrPredicateType，我想你可能想要.AndPredicateType？

@pbasdf 感谢您发现谓词问题，但重新加载应用后对象仍然没有出现。另外，我检查了对象在保存之前不是 nil

objects 我指的是 fetch 返回的数组。如果由于某种原因 fetch 出现错误，objects 将为 nil，并且您的 if let results = objects 中的所有内容都将被跳过。

【参考方案1】：

问题是我使用的是可变类型，所以更改没有调用 setter 方法。我更改了代码以创建对象的副本，以便识别更改：

let days1 = results[0].valueForKey("days") as! NSMutableArray
let days = days1.mutableCopy() as! NSMutableArray 

days.addObject(NSDate())
let person = results[0] as! People

person.setValue(days, forKey: "days”)