CoreData Swift：如何保存和加载数据？

Question

I'm writing an iOS game in Swift, and I wanted to include a highscore label at the end. I think that the saving function is correct, but the load one is the one which is giving me problems. I already created an entity ("BestScores") and the attributes ("classicBestScoreTF"):

To save the highscore:

var bestscore25 = 1000
var score: int

func savescore() {    
    var appDel: AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
    var context:NSManagedObjectContext = appDel.managedObjectContext!
    var score25: AnyObject! = NSEntityDescription.insertNewObjectForEntityForName("BestScores", inManagedObjectContext: context) as NSManagedObject
    score25.setValue(score, forKey: "classicBestScoreTF")
    context.save(nil)
}

func loadscore() {
    var appDel: AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
    var context:NSManagedObjectContext = appDel.managedObjectContext!
    bestScore25 = valueForKey("classicBestScoreTF") as Int
}

func endgame() {

    if score > bestScore25 {
        savescore()
        loadscore()
        bestScoreLabel.text = "Best Score: \(bestScore25)"
    }

    if score < bestscore {            
        loadscore()
        bestScoreLabel.text = "Best Score: \(bestScore25)"
    }    
}

It's not working :( Please help!

Answer 1

Saving data:

var person = NSEntityDescription.insertNewObjectForEntityForName("Person", 
inManagedObjectContext: self.managedObjectContext!) as Person
person.name = "Mary"
person.age = Float(arc4random() % 100)

var error : NSError? = nil
if !self.managedObjectContext!.save(&error) {
    NSLog("Unresolved error \(error), \(error!.userInfo)")
    abort()
}

Loading data:

var error: NSError? = nil
var fReq: NSFetchRequest = NSFetchRequest(entityName: "Frases")    
fReq.predicate = NSPredicate(format: "id contains[c] %@", String(day))
var sorter: NSSortDescriptor = NSSortDescriptor(key: "id" , ascending: false)
fReq.sortDescriptors = [sorter]
fReq.returnsObjectsAsFaults = false
let result : [AnyObject] = self.managedObjectContext!.executeFetchRequest(fReq, error:&error)!

Answer 2

For saving data, you should be using:

context.insertNewObjectForEntityForName(...)

And the same when you are loading data, it should be:

context.valueForKey(...)

However, I am not sure if that is even the correct syntax, as you may need to get an array of the entities and then get the object at index 0. On that note why are you using core data for high scores? You might want to look into user defaults or icloud, Core data is designed more for databases

Answer 3

Updated for swift:

used below simple code for load, insert, delete date;

import UIKit
import CoreData

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate{

    // MARK:- Variable Declarations

    @IBOutlet weak var mTableView: UITableView!
    var manageObjectContext: NSManagedObjectContext!
    var eventArray = [Event]()

    // MARK:- ViewController LifeCycle Methods

    override func viewDidLoad() {
        super.viewDidLoad()
        self.title = "Event Reminder"
        manageObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
        self.loadSaveData()
    }

    override func viewWillAppear(_ animated: Bool) {
        // Remove empty cell from tableview
        mTableView.tableFooterView = UIView(frame: .zero)
    }

    // MARK:- TableView DataSource and Delegate Methods

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return eventArray.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: "ViewControllerTableViewCell")! as! ViewControllerTableViewCell
        cell.layer.cornerRadius = 05

        let eventArrayItem = eventArray[indexPath.row]

        if let eventImage = UIImage(data: (eventArrayItem.event_image! as Data)){
            cell.mImageView.image = eventImage
        }

        cell.mEventHeadingLabel.text = eventArrayItem.event_heading
        cell.mShortDescriptionLabel.text = eventArrayItem.event_description

        return cell
    }

    // To delete Particular cell/row from tableview
    func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {

        let eventArrayItem = eventArray[indexPath.row]

        if editingStyle == .delete {
            manageObjectContext.delete(eventArrayItem)

            do {
                try manageObjectContext.save()
            } catch let error as NSError {
                print("Error While Deleting Note: \(error.userInfo)")
            }
        }
        self.loadSaveData()
    }

    // MARK:- IBAction Methods

    @IBAction func actionOnPlusButton(_ sender: Any) {
        let imagePicker = UIImagePickerController()
        imagePicker.sourceType = .photoLibrary
        imagePicker.delegate = self
        self.present(imagePicker, animated: true, completion: nil)
    }

    // MARK:- ImagePicker Delegate Methods

    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        picker.dismiss(animated: true, completion: nil)
    }

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {

        if let mImage = info[UIImagePickerControllerOriginalImage] as? UIImage{
            picker.dismiss(animated: true, completion: { 
                self.createEventItemWith(selectedImage: mImage)
            })
        }
    }

    // MARK:- Instance Methods

    func createEventItemWith(selectedImage: UIImage)  {

        let eventItem = Event(context: manageObjectContext)

        let alertController = UIAlertController(title: "Add Event", message: "Enter event and it's description", preferredStyle: .alert)

        let saveAction = UIAlertAction(title: "Save", style: .default, handler: {
            alert -> Void in

            let eventNameTextField = alertController.textFields![0] as UITextField
            let descriptionTextField = alertController.textFields![1] as UITextField

            print("firstName \(String(describing: eventNameTextField.text)), secondName \(String(describing: descriptionTextField.text))")

            if eventNameTextField.text != "" || descriptionTextField.text != ""{

                eventItem.event_heading = eventNameTextField.text
                eventItem.event_description = descriptionTextField.text
                eventItem.event_image = NSData(data: UIImageJPEGRepresentation(selectedImage, 0.3)!)

                do{
                    try self.manageObjectContext.save()
                    self.loadSaveData()
                }catch{
                    print("Could not save data: \(error.localizedDescription)")
                }

            }else{
                self.showAlertMessageToUser(title: "Alert", messageToUser: "Fields should not be empty, Please enter given info...")
            }
        })

        let cancelAction = UIAlertAction(title: "Cancel", style: .default, handler: {
            (action : UIAlertAction!) -> Void in
                self.manageObjectContext.reset()
        })

        alertController.addTextField { (textField : UITextField!) -> Void in
            textField.placeholder = "Enter event Name"
        }
        alertController.addTextField { (textField : UITextField!) -> Void in
            textField.placeholder = "Enter event description in short"
        }

        alertController.addAction(saveAction)
        alertController.addAction(cancelAction)

        self.present(alertController, animated: true, completion: nil)
    }

    func showAlertMessageToUser(title: String, messageToUser: String)  {
        let alert = UIAlertController(title: title, message: messageToUser, preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
        self.present(alert, animated: true, completion: nil)
    }

    func loadSaveData()  {
        let eventRequest: NSFetchRequest<Event> = Event.fetchRequest()
        do{
            eventArray = try manageObjectContext.fetch(eventRequest)
            self.mTableView.reloadData()
        }catch
        {
            print("Could not load save data: \(error.localizedDescription)")
        }
    }
}

Answer 4

Swift 5

Step 1. Create Simple app with CoreData option

Step 2. Open .xcdatamodeld file and add Entity , Attributes this way

Step 3. your AppDelegate should have Core Data stack methods

Step 4. Make sure you have swift code snipe as following

import UIKit
import CoreData

class ViewController: UIViewController {

    // MARK: Variables declearations
    let appDelegate = UIApplication.shared.delegate as! AppDelegate //Singlton instance
    var context:NSManagedObjectContext!

    // MARK: View Controller life cycle methods
    override func viewDidLoad() {
        super.viewDidLoad()

        openDatabse()
    }

    // MARK: Methods to Open, Store and Fetch data
    func openDatabse()
    {
        context = appDelegate.persistentContainer.viewContext
        let entity = NSEntityDescription.entity(forEntityName: "Users", in: context)
        let newUser = NSManagedObject(entity: entity!, insertInto: context)
        saveData(UserDBObj:newUser)
    }

    func saveData(UserDBObj:NSManagedObject)
    {
        UserDBObj.setValue("RDC", forKey: "username")
        UserDBObj.setValue("1234", forKey: "password")
        UserDBObj.setValue("21", forKey: "age")

        print("Storing Data..")
        do {
            try context.save()
        } catch {
            print("Storing data Failed")
        }

        fetchData()
    }

    func fetchData()
    {
        print("Fetching Data..")
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
        request.returnsObjectsAsFaults = false
        do {
            let result = try context.fetch(request)
            for data in result as! [NSManagedObject] {
                let userName = data.value(forKey: "username") as! String
                let age = data.value(forKey: "age") as! String
                print("User Name is : "+userName+" and Age is : "+age)
            }
        } catch {
            print("Fetching data Failed")
        }
    }
}

Step 5. Run on Device and see log for core data results

Answer 5

import UIKit import CoreData

class ViewController: UIViewController {

let nameTxt: UITextField = {

    let td = UITextField()
    td.translatesAutoresizingMaskIntoConstraints = false
    td.placeholder = "Enter Id"
    td.borderStyle = .line
    td.layer.borderWidth = 1
    td.layer.borderColor = UIColor.lightGray.cgColor
    return td
}()

let doneBt: UIButton = {

    let bt = UIButton()
    bt.translatesAutoresizingMaskIntoConstraints = false
    bt.setTitle("DONE", for: .normal)
    bt.setTitleColor(.white, for: .normal)
    bt.addTarget(self, action: #selector(handleDoneBt), for: .touchUpInside)
    bt.backgroundColor = UIColor.blue
    return bt
}()

@objc func handleDoneBt() {

     saveData()
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    view.backgroundColor = .white

    setupView()
    setupLayout()

}


func saveData() {

    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}

    let manageContent = appDelegate.persistentContainer.viewContext

    let userEntity = NSEntityDescription.entity(forEntityName: "Users", in: manageContent)!

    let users = NSManagedObject(entity: userEntity, insertInto: manageContent)

    users.setValue(1, forKeyPath: "id")
    users.setValue(nameTxt.text, forKeyPath: "name")
    users.setValue(123, forKeyPath: "mobile")


    do{
        try manageContent.save()
    }catch let error as NSError {

        print("could not save . \(error), \(error.userInfo)")
    }

    fetchData()
}

func fetchData() {

    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}
     let manageContent = appDelegate.persistentContainer.viewContext
     let fetchData = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")

    do {

        let result = try manageContent.fetch(fetchData)

        for data in result as! [NSManagedObject]{

             print(data.value(forKeyPath: "id") as Any)
             print(data.value(forKeyPath: "name") as Any)
        }
    }catch {
        print("err")
    }
}

func setupView() {

    view.addSubview(nameTxt)
    view.addSubview(doneBt)
}
func setupLayout(){

    NSLayoutConstraint.activate([

            nameTxt.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            nameTxt.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            nameTxt.widthAnchor.constraint(equalToConstant: 160),
            nameTxt.heightAnchor.constraint(equalToConstant: 30),

            doneBt.topAnchor.constraint(equalTo: nameTxt.bottomAnchor,constant: 6),
            doneBt.leftAnchor.constraint(equalTo: nameTxt.leftAnchor,constant: 8),
            doneBt.widthAnchor.constraint(equalToConstant: 120),
            doneBt.heightAnchor.constraint(equalToConstant: 36)
        ])
}

}

DISPLAY IN TABLEVIEW

func fetchData() {

    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}
    let manageContent = appDelegate.persistentContainer.viewContext
    let fetchData = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")        
    do {

        let result = try manageContent.fetch(fetchData)
        allData = result as! [NSManagedObject]
        tbl.reloadData()
    }catch {
        print("err")
    }
}

var allData = [NSObject]()

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return allData.count }

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: cellId, for: indexPath) as! tblCell
    cell.lbl.text = allData[indexPath.row].value(forKey: "name") as? String
    return cell
}

func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {

    if editingStyle == .delete {
        let task = allData[indexPath.row]
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}

        let manageContent = appDelegate.persistentContainer.viewContext

        manageContent.delete(task as! NSManagedObject)
        (UIApplication.shared.delegate as! AppDelegate).saveContext()

        do {
            try manageContent.save()
        } catch {
            print("Fetching Failed")
        }
    }
    fetchData()
}

Answer 6

Operations with CoreData

import CoreData


public class ItemCoreDataStorage {
    
    let context: NSManagedObjectContext
    
    init(context: NSManagedObjectContext) {
        self.context = context
    }
    
    func save(_ items: [Item]) {
        
        cashbackItems.forEach({ item in
            let moItem = MOCashback(context: context)
            moItem.a = item.a
            moItem.b = item.b
        })
        
        do {
            try context.save()
        } catch {
            //Error handling
        }
        
    }
    
    func fetch() -> [MOItem] {
        do {
            let moItems: [MOItem] = try context.fetch(MOItem.fetchRequest())
            return moItems
        } catch {
            //Error handling
        }
    }
    
    func fetchedResultsController() -> NSFetchedResultsController<MOItem> {
        
        let fetchRequest: NSFetchRequest< MOItem > = MOCashback.fetchRequest()
        fetchRequest.sortDescriptors = [NSSortDescriptor(key: "a", ascending: true)]
        let frc = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
        
        return frc
    }
    
    func delete() {

        self.fetch()
            .forEach({ context.delete($0)})
        do {
            try context.save()
        }
        catch {
            //Error handling
        }

    }
}

• Please note that you can for example use bunch for delete items but it will not be managed by FRC.

• Also fetchRequest.sortDescriptors is mandatory

Answer 7

import UIKit import CoreData

class ViewController: UIViewController {

@IBOutlet weak var nameREA: UITextField!

@IBOutlet weak var emailREA: UITextField!
@IBOutlet weak var addressREA: UITextField!



@IBOutlet weak var schoolREA: UITextField!


@IBOutlet weak var departmentREA: UITextField!
@IBOutlet weak var coursREA: UITextField!

let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext



override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}
@IBAction func saveA(_ sender: Any) {
    
    let stdA = NSEntityDescription.insertNewObject(forEntityName: "StudentsFR", into: context)
    stdA.setValue(self.nameREA.text, forKey: "st_name")
    stdA.setValue(self.emailREA.text, forKey: "st_email")
    stdA.setValue(self.addressREA.text, forKey: "st_address")
    stdA.setValue(self.schoolREA.text, forKey: "st_school")
    stdA.setValue(self.departmentREA.text, forKey: "st_department")
    stdA.setValue(self.coursREA.text, forKey: "st_course")
    do{
        try context.save()
        self.nameREA.text = ""
        self.emailREA.text = ""
        self.addressREA.text = ""
        self.schoolREA.text = ""
        self.departmentREA.text = ""
        self.coursREA.text = ""
    } catch{
        print("error")
    }
    
}
@IBAction func showA(_ sender: Any) {
    
    let storybd = UIStoryboard(name: "Main", bundle: nil)
    let stdA = storybd.instantiateViewController(withIdentifier: "tblA")as!tblviewAViewController
    self.navigationController?.pushViewController(stdA, animated: true)
        }

}

Answer 8

import UIKit

class tableviewAViewController: UIViewController,UITableViewDelegate,UITableViewDataSource {

@IBOutlet weak var tablREA: UITableView!
var context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

var studentarray:[Studentsdet] = []

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return studentarray.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "tblA", for: indexPath)
    let onrecord = studentarray[indexPath.row]
    cell.textLabel?.text = onrecord.name_std! + "" + onrecord.age_std! + "" + onrecord.department_std! + "" + onrecord.course_std!
    
    return cell
}
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete{
        let std = studentarray[indexPath.row]
        context.delete(std)
        (UIApplication.shared.delegate as! AppDelegate).saveContext()
        do{
            studentarray = try context.fetch(Studentsdet.fetchRequest())
            
        }catch
        {
            print("error")
            
        }
   }
    
    
    tableView.reloadData()
}
func fetchdata()
{
    do{
        studentarray = try context.fetch(Studentsdet.fetchRequest())
    }catch{
        print("error")
    }
}

override func viewDidLoad() {
    super.viewDidLoad()

    self.fetchdata()
    self.tablREA.reloadData()
    
    
    // Do any additional setup after loading the view.
}