一对多关系核心数据只保存最后一个对象。其他人不见了

Posted 2023-03-12

【中文标题】一对多关系核心数据只保存最后一个对象。其他人不见了

【英文标题】：One-To-Many relationship core data saves only last object. Others are missing

【发布时间】：2017-05-27 06:21:23

【问题描述】：

我正在尝试将一些对象保存到 NSSet，但最后一个对象仅被保存。我的示例源代码是

func saveData()
  let appDelegate =
    UIApplication.shared.delegate as! AppDelegate
  let managedContext = appDelegate.managedObjectContext

  let personEentity =  NSEntityDescription.entity(forEntityName: "PersionalDetails",
                                         in:managedContext)
  let person = PersionalDetails(entity: personEentity!,
                    insertInto: managedContext)

  let favourateEentity =  NSEntityDescription.entity(forEntityName: "Favourites",
                                                in:managedContext)
  let favourate = Favourites(entity: favourateEentity!,
                              insertInto: managedContext)

  person.name = "Ragul"
  person.age = 28
  person.mobileNumber = "0000000000"
  person.sex = "male"
  for i in 0..<5
    favourate.movie = "Some movie" + "\(i)"
    favourate.actor = "Some actor" + "\(i)"
    favourate.song = "some song" + "\(i)"
    favourate.person = person
  
  do 
    try managedContext.save()
   catch let error as NSError  
    print("Could not save \(error), \(error.userInfo)")
  
 

请指导我摆脱这个错误。

【参考方案1】：

当您在 for 循环中设置同一对象的属性时，您只需要获得最后一个对象您需要做的是每次在 for 循环的迭代中您需要创建 Favourites 的新实例然后它将存储您创建的所有对象不是唯一的最后一个。

for i in 0..<5
    let favourate = Favourites(entity: favourateEentity!, insertInto: managedContext)
    favourate.movie = "Some movie" + "\(i)"
    favourate.actor = "Some actor" + "\(i)"
    favourate.song = "some song" + "\(i)"
    favourate.person = person

【讨论】：

@Ragul 欢迎朋友 :)