保存/获取 CoreData 关系 Swift 3
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【中文标题】保存/获取 CoreData 关系 Swift 3【英文标题】:Saving/Fetching CoreData Relationships Swift 3 【发布时间】:2017-06-22 21:29:02 【问题描述】:我正在制作一个用于学习的预算应用程序,我有几个关于在 CoreData 中存储和获取实体的问题。
我有两个实体“预算”和“费用”。
每个预算都有自己的费用。例如,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。然后加上费用。
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 Expenses 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,以便我可以在 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。
【问题讨论】:
【参考方案1】:可能有几种方法可以实现这一目标。最直接的方法是对expense
使用有序关系。
为此,
在 DataModel 编辑器中打开expense
关系属性。
检查订购选项
那么budget.expense
将不是Set
,而是OrderedSet
,你不需要将其转换为Array
,而是直接通过索引访问。
【讨论】:
漂亮!谢谢!【参考方案2】:浏览器控制器 1: =====================>
导入核心数据
类视图控制器: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
视图控制器 2:
=====================>
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)
override func prepare(for segue: UIStoryboardSegue, sender: Any?)
if let newlabel = txt_pwd.text
str1 = newlabel as NSString
【讨论】:
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