ios - 一对多关系核心数据只保存最后一个对象。别人不见了

Question

我试图将一些对象保存到 NSSet 但最后一个对象只被保存。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)")
  }
 }

请指导我走出这个错误。

Answer 1

当您在 for 循环中设置同一对象的属性时，您只需要最后一个对象，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，而不是唯一的最后一个对象。

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
}