Swift 3 核心数据删除对象

Question

不幸的是，新的核心数据语义让我抓狂。我之前的问题有一个干净的代码，由于头文件的自动生成不正确而无法正常工作。现在我继续删除对象。我的代码似乎很简单：

func deleteProfile(withID: Int) {
    let fetchRequest: NSFetchRequest<Profile> = Profile.fetchRequest()
    fetchRequest.predicate = Predicate.init(format: "profileID==\(withID)")
    let object = try! context.fetch(fetchRequest)
    context.delete(object)
}

我用 print(object) 而不是 context.delete(object) 进行了 "hard" 调试，它向我展示了正确的对象。所以我只需要删除它。

P.S。没有deleteObject。现在 NSManagedContext 只有 public func delete(_ sender: AnyObject?)

Answer 1

获取的结果是一个 array 托管对象，在你的例子中 [Event]，所以可以枚举数组，删除所有匹配的对象。示例（使用 try? 而不是 try! 以避免在这种情况下崩溃提取错误):

if let result = try? context.fetch(fetchRequest) {
    for object in result {
        context.delete(object)
    }
}

do {
    try context.save()
} catch {
    //Handle error
}

如果不存在匹配的对象，则提取成功，但结果数组为空。

注意： 在您的代码中，object 具有类型 [Event]，因此在

context.delete(object)

编译器调用

public func delete(_ sender: AnyObject?)

NSObject 的方法而不是预期的

public func delete(_ object: NSManagedObject)

NSManagedObjectContext 的方法。这就是你的代码编译的原因但在运行时失败。

Answer 2

删除核心数据对象swift3

// MARK: Delete Data Records

func deleteRecords() -> Void {
    let moc = getContext()
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Person")

     let result = try? moc.fetch(fetchRequest)
        let resultData = result as! [Person]

        for object in resultData {
            moc.delete(object)
        }

        do {
            try moc.save()
            print("saved!")
        } catch let error as NSError  {
            print("Could not save \(error), \(error.userInfo)")
        } catch {

        }

}

// MARK: Get Context

func getContext () -> NSManagedObjectContext {
    let appDelegate = UIApplication.shared.delegate as! AppDelegate
    return appDelegate.persistentContainer.viewContext
}

Answer 3

这里的诀窍是在删除对象后保存上下文。

let fetchRequest: NSFetchRequest<Profile> = Profile.fetchRequest()
fetchRequest.predicate = Predicate.init(format: "profileID==\(withID)")
let objects = try! context.fetch(fetchRequest)
for obj in objects {
    context.delete(obj)
}

do {
    try context.save() // <- remember to put this :)
} catch {
    // Do something... fatalerror
}

希望对大家有所帮助。

Answer 4

Swift 4 实体不使用字符串

let fetchRequest: NSFetchRequest<Profile> = Profile.fetchRequest()
fetchRequest.predicate = Predicate.init(format: "profileID==\(withID)")

do {
    let objects = try context.fetch(fetchRequest)
    for object in objects {
        context.delete(object)
    }
    try context.save()
} catch _ {
    // error handling
}

Answer 5

func deleteRecords() {
    let delegate = UIApplication.shared.delegate as! AppDelegate
    let context = delegate.persistentContainer.viewContext

    let deleteFetch = NSFetchRequest<NSFetchRequestResult>(entityName: "nameofentity")
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: deleteFetch)

    do {
        try context.execute(deleteRequest)
        try context.save()
    } catch {
        print ("There was an error")
    }
}

Answer 6

Swift 4.1、4.2 和 5.0

     let appDelegate = UIApplication.shared.delegate as! AppDelegate
     let context = appDelegate.persistentContainer.viewContext
     let requestDel = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
     requestDel.returnsObjectsAsFaults = false
  // If you want to delete data on basis of some condition then you can use NSPredicate
  //  let predicateDel = NSPredicate(format: "age > %d", argumentArray: [10])
  // requestDel.predicate = predicateDel


     do {
          let arrUsrObj = try context.fetch(requestDel)
          for usrObj in arrUsrObj as! [NSManagedObject] { // Fetching Object
              context.delete(usrObj) // Deleting Object
         }
     } catch {
          print("Failed")
     }

    // Saving the Delete operation
     do {
         try context.save()
     } catch {
         print("Failed saving")
     }

Answer 7

从核心数据中删除对象

let entity = NSEntityDescription.entity(forEntityName: "Students", in: managedContext)
        let request = NSFetchRequest<NSFetchRequestResult>()
        request.entity = entity
        if let result = try? managedContext.fetch(request) {
            for object in result {
                managedContext.delete(object as! NSManagedObject)
            }
            txtName.text = ""
            txtPhone.text = ""
            txt_Address.text = ""
            labelStatus.text = "Deleted"

        }

Answer 8

在 Swift 5、4.2

中使用查询删除核心数据对象

let fetchRequest = NSFetchRequest<Your_Model>(entityName: "Your_Entity_Name")
fetchRequest.predicate = NSPredicate(format: "any your_key == %d", your_value)

希望这对某人有所帮助

Swift 3 核心数据删除对象

Swift 3 Core Data Delete Object

ios

swift

core-data

swift3