一对多关系CoreData Swift

Posted 2023-03-04

【中文标题】一对多关系CoreData Swift

【英文标题】：One to many relationship CoreData Swift

【发布时间】：2015-01-10 15:18:08

【问题描述】：

Core Data 在大多数情况下都非常有效。当我点击 name first VC (Items) 并 performSeque to the second VC (Costs) 时，我可以看到 costName 和其他数据。但是当我在第一个 VC 中添加第二个名字时，我可以看到与名字相同的数据。

我正在尝试建立一对多的关系。

我有 2 个数据模型：

import Foundation
import CoreData

@objc(Items)
class Items: NSManagedObject 

   @NSManaged var count: NSNumber
   @NSManaged var name: String
   @NSManaged var cost: NSSet



import Foundation
import CoreData

@objc(Costs)
class Costs: NSManagedObject 

  @NSManaged var costsDate: NSDate
  @NSManaged var costsName: String
  @NSManaged var costsValue: NSNumber
  @NSManaged var account: Items

这是addAccount（第一个 VC 的名称）的保存操作：

@IBAction func saveButtonPressed(sender: UIBarButtonItem) 

    let appDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
    var managedObjectContext = appDelegate.managedObjectContext
    let entityDescription = NSEntityDescription.entityForName("Items", inManagedObjectContext: managedObjectContext!)

    let account = Items(entity: entityDescription!, insertIntoManagedObjectContext: managedObjectContext!)

    account.name = cellOneNameTextField.text
    if cellTwoCountTextField.text.isEmpty 

     else 

    account.count = (cellTwoCountTextField.text).toInt()!
    
    // Saving data
    appDelegate.saveContext()

    var request = NSFetchRequest(entityName: "Items")
    var error:NSError? = nil

    var results:NSArray = managedObjectContext!.executeFetchRequest(request, error: &error)!

    self.navigationController?.popViewControllerAnimated(true)

这是addCost的保存动作：

    @IBAction func saveButtonTapped(sender: UIBarButtonItem) 

    // CoreData Access
    let appDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
    var managedObjectContext = appDelegate.managedObjectContext
    let entityDescription = NSEntityDescription.entityForName("Costs", inManagedObjectContext: managedObjectContext!)

    let cost = Costs(entity: entityDescription!, insertIntoManagedObjectContext: managedObjectContext!)

    cost.costsName = cellThreeNoteTextField.text
    cost.costsValue = (cellOnePriceTextField.text).toInt()!
    cost.costsDate = datePicker.date

    // Saving data
    appDelegate.saveContext()

    var request = NSFetchRequest(entityName: "Costs")
    var error:NSError? = nil

    var results:NSArray = managedObjectContext!.executeFetchRequest(request, error: &error)!

    for res in results 
        println(res)

    
    delegate?.refreshTable()
    self.navigationController?.popViewControllerAnimated(true)

【参考方案1】：

我不知道你是否在某个地方这样做，但你的Items 应该使用来自Items 的cost 变量将Count 对象附加到自身。类似的东西：

let account = Items(...)     
let cost = Cost(...)   
account.cost.addObject(cost)//and changing your var cost:NSSet into var cost:NSMutableSet
//then save Items

（addObject没试过，原理你懂的）