保存/获取CoreData关系Swift 3

Question

我正在制作一个预算应用程序用于学习目的，我有一些关于在CoreData中存储和获取实体的问题。

我有两个实体“预算”和“费用”。

每份预算都有自己的费用。作为一个例子，我可以有一个“娱乐”预算，它可以有“保龄球”和“电影”等费用。

我可以创建预算并保存。然后增加费用。

let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let expense = Expense(context: context)
.
. // Filling out the expense here
.
budget?.addToExpense(expense)
(UIApplication.shared.delegate as! AppDelegate).saveContext()

然后我检索费用集合并在TableView中显示商店名称

// Inside cellForRowAt
let cell = UITableViewCell(style: .default, reuseIdentifier: "cell")
let myArray = Array((budget?.expense)!)
cell.textLabel?.text = (myArray[indexPath.row] as! Expense).store
return cell

到目前为止一切顺利。我的问题是，当我存储费用时，它存储在一个集合中。这意味着当我检索该集合并将其类型转换为数组时，顺序是随机的。

我想要的是存储费用并以这样的方式检索它们，即我可以在TableView中以FIFO顺序显示费用。换句话说，我在预算中添加的第一笔费用应该是表格视图中的第一个元素，依此类推。

Answer 1

有几种方法可以实现这一目标。最直接的方法是使用expense的有序关系。

要做到这一点，

• 在DataModel编辑器中打开expense关系属性。
• 检查订购选项

然后budget.expense将不是Set，而是OrderedSet，您不需要将其转换为Array，而是直接通过索引访问它。

Answer 2

VIEWCONTROLLER 1： =====================＆GT;

导入CoreData

类ViewController：UIViewController {

@IBOutlet weak var txt_user: UITextField!





@IBOutlet weak var txt_password: UITextField!



var result = NSArray()



override func viewDidLoad() {

    super.viewDidLoad()

    // Do any additional setup after loading the view, typically from a nib.



    txt_password.isSecureTextEntry = true

}







@IBAction func login_action(_ sender: Any)

{

   if(txt_user.text == "" || txt_password.text == "")

   {

    let alert = UIAlertController(title: "info", message: "fields are empty", preferredStyle: .alert)

    let ok = UIAlertAction(title: "OK", style: .default, handler: nil)

    alert.addAction(ok)

    self.present(alert, animated: true, completion: nil)



    }

    else

   {

    self.CheckForUserNameAndPasswordMatch(empName: txt_user.text! , empPwd: txt_password.text!)

    }





}



func CheckForUserNameAndPasswordMatch(empName:String,empPwd:String)

{

    let app = UIApplication.shared.delegate as! AppDelegate

    let context = app.persistentContainer.viewContext





    let fetchdata = NSFetchRequest<NSManagedObject>(entityName: "Employee")

    let predicate = NSPredicate(format: "empName = %@",empName)

    fetchdata.predicate = predicate

    do

    {

        self.result = try context.fetch(fetchdata as! NSFetchRequest<NSFetchRequestResult>)as NSArray

        if result.count>0

        {

            let objcetEntity = result.firstObject as! Employee





            if objcetEntity.empName == empName && objcetEntity.empPwd == empPwd

            {

                print("Login Successfully")

                // Entered Username & password matched

            }

            else

            {

                print("Wrong password/username")



                //Wrong password/username

            }



        }

    }

    catch let error as NSError

    {

        print("error",error.localizedDescription)

    }

}





 @IBAction func unwindToVC1(sender:UIStoryboardSegue)

 {

    if sender.source is ViewController2

    {

        let secvc = sender.source as! ViewController2

        txt_password.text = secvc.str1! as String

    }



}

VIEWCONTROLLER 2：

=====================＆GT;

类ViewController2：UIViewController，UITextFieldDelegate {

@IBOutlet weak var txt_name: UITextField!



@IBOutlet weak var txt_mail: UITextField!



@IBOutlet weak var txt_pwd: UITextField!



@IBOutlet weak var txt_cpwd: UITextField!



@IBOutlet weak var txt_phone: UITextField!



@IBOutlet weak var err: UILabel!



var str1:NSString!

var str2:NSString!



//var update:NSManagedObject!







override func viewDidLoad() {

    super.viewDidLoad()



    /*if(update != nil)

    {

    txt_name.text = update.value(forKey: "empName") as? String

    txt_mail.text = update.value(forKey: "empMail") as? String

    txt_pwd.text = update.value(forKey: "empPwd") as? String

    txt_cpwd.text = update.value(forKey: "empCpwd") as? String

    txt_phone.text = update.value(forKey: "empPhone") as? String

    }*/



    txt_pwd.isSecureTextEntry = true

    txt_cpwd.isSecureTextEntry = true





}



override func viewWillAppear(_ animated: Bool)

{

    txt_name.becomeFirstResponder()

}









@IBAction func regis_clicked(_ sender: Any)

{



    if(txt_name.text == "" || txt_mail.text == "" || txt_pwd.text == "" || txt_cpwd.text == "" || txt_phone.text == "" )

    {

        let alert = UIAlertController(title: "information", message: "fields are empty", preferredStyle: .alert)

        let ok = UIAlertAction(title: "OK", style: .default, handler:

        {

           (actionsheet) in



            if(self.txt_name.text == "")

            {

                self.txt_name.becomeFirstResponder()

            }

            if(self.txt_mail.text == "")

            {

                self.txt_mail.becomeFirstResponder()

            }

            if(self.txt_pwd.text == "")

            {

                self.txt_pwd.becomeFirstResponder()

            }

            if(self.txt_cpwd.text == "")

            {

                self.txt_cpwd.becomeFirstResponder()

            }

            if(self.txt_phone.text == "")

            {

                self.txt_phone.becomeFirstResponder()

            }

        })



        let cancel = UIAlertAction(title: "cancel", style: .default, handler: nil)

        alert.addAction(ok)

        alert.addAction(cancel)



        self.present(alert, animated: true, completion: nil)

    }



    else if(txt_pwd.text != txt_cpwd.text)

    {



        let alert1 = UIAlertController(title: "information", message: "password mismatched", preferredStyle: .alert)

        let ok = UIAlertAction(title: "OK", style: .default, handler:nil)

        let cancel = UIAlertAction(title: "cancel", style: .default, handler: nil)

        alert1.addAction(ok)

        alert1.addAction(cancel)

        self.present(alert1, animated: true, completion: nil)

    }

    else

    {



        let app = UIApplication.shared.delegate as! AppDelegate



        let context = app.persistentContainer.viewContext



        let newuser = NSEntityDescription.insertNewObject(forEntityName: "Employee", into: context)

        newuser.setValue(txt_name.text, forKey: "empName")

        newuser.setValue(txt_mail.text, forKey: "empMail")

         newuser.setValue(txt_pwd.text, forKey: "empPwd")

         newuser.setValue(txt_cpwd.text, forKey: "empCpwd")

         newuser.setValue(txt_phone.text, forKey: "empPhone")



        do

        {

            try context.save()

        }

        catch let error as NSError

        {

            print("error",error.localizedDescription)

        }



    }

   // self.navigationController?.popViewController(animated: true)

    performSegue(withIdentifier: "unwind", sender: self)

}

覆盖func prepare（对于segue：UIStoryboardSegue，sender：Any？）

{

    if let newlabel = txt_pwd.text

    {

        str1 = newlabel as NSString

    }

}