我正在尝试将数据添加到应用程序的Core Data中。当我保存它而不检查它是否已经存在时,它可以正常工作。但是我在核心数据中没有什么重复的,所以我要获取所有具有实体名称的实体,我会先尝试添加,然后检查它是否为0,否则添加否。但是在尝试保存时,我总是收到错误消息。如果有人可以帮助我解决这个问题。
这是我的检查功能:
func entityExists(name: String) -> Bool {
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "name")
fetchRequest.includesSubentities = false
var entitiesCount = 0
do {
entitiesCount = try coreDataController.mainContext.count(for: fetchRequest)
}
catch {
print("error executing fetch request: \(error)")
}
if entitiesCount == 0{
return true
} else {
return false
}
}
这是我保存数据时的代码。
if entityExists(name: (scrimmagePassedOver?.name)!) == true{
coreDataController.saveContext()
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "load"), object: nil)
let alert = UIAlertController(title: "Saved!", message: "You have saved your Scrimmage.", preferredStyle: UIAlertControllerStyle.alert)
// add an action (button)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
self.present(alert, animated: true, completion: nil)
} else {
let alert = UIAlertController(title: "hey", message: "You have saved this Scrimmage before.", preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
self.present(alert, animated: true, completion: nil)
}
答案 0 :(得分:0)
您可以像这样从您的核心数据中查看记录:
func checkRecordExists(entity: String,uniqueIdentity: String,idAttributeName:String) -> Bool {
let context = getManagedObjectContext()
let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: entity)
fetchRequest.predicate = NSPredicate(format: "\(idAttributeName) CONTAINS[cd] %@", createdDate)
var results: [NSManagedObject] = []
do {
results = try context.fetch(fetchRequest)
}
catch {
print("error executing fetch request: \(error)")
}
return results.count > 0
}
和managedObjectContext
是:
func getManagedObjectContext() -> NSManagedObjectContext{
let delegate = UIApplication.shared.delegate as? AppDelegate
return delegate!.persistentContainer.viewContext
}
如果得到false
,请保存。