所以我有我的tableview
,当我对行重新排序时,它会更新tableview
和所有内容,但不会保存到core data
。
func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let movedCampSites = itemName[sourceIndexPath.item]
itemName.remove(at: sourceIndexPath.item)
itemName.insert(movedCampSites, at: destinationIndexPath.item)
context.delete(itemName[sourceIndexPath.row])
context.insert(itemName[destinationIndexPath.row])
do
{
try context.save()
}
catch
{
print("Could not move rows")
}
}
例如,如果我注释掉并运行它,一切都会进行到context.insert(itemName[destinationIndexPath.row])
,它将移动行并删除该行并保存到core data
,但是context.insert
不会保存新的行位置。由于某种原因,它正在运行我的catch块,因为我收到错误无法移动行。
这里是控制台中的某些错误。
2018-07-22 09:27:01.884925-0700搜索栏核心数据[67957:5383630] [错误]错误:(1555)唯一约束失败:ZTITLE.Z_PKCoreData:错误:(1555)唯一约束失败:ZTITLE.Z_PK无法移动行
谢谢。
这是我对这个问题的看法:
就像“ vadian”说的那样,当您创建一个对象时,您会为附加到核心数据的数组添加一个属性,像这样,
var itemsArray: [NSManagedObject] = []
save(sortOrder: itemsArray.count, item: itemTextField.text!) //Calling the save method wherever you need to, catching for example a UITextField user input
private func save(sortOrder: Int, item: String) {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
let context = appDelegate.persistentContainer.viewContext
guard let entity = NSEntityDescription.entity(forEntityName: "CoreDataBaseName", in: context) else { return }
let itemManagedObject = NSManagedObject(entity: entity, insertInto: context)
itemManagedObject.setValue(sortOrder, forKeyPath: "sortOrder")
itemManagedObject.setValue(item, forKeyPath: "item")
do {
try context.save()
itemsArray.append(itemManagedObject)
} catch let error as NSError {
print("Could not save item to Core Data: \(error)")
}
}
然后我们进入tableView的moveRowAt方法,
override func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
let context = appDelegate.persistentContainer.viewContext
let movedItem = itemsArray[sourceIndexPath.row]
itemsArray.remove(at: sourceIndexPath.row)
itemsArray.insert(movedItem, at: destinationIndexPath.row)
//This 'for-in loop' is at the heart of the solution
for (i, item) in itemsArray.enumerated() {
item.setValue(i, forKey: "sortOrder")
}
do {
try context.save()
} catch let error as NSError {
print("Could not save/persist Core Data items in moveRowAt: \(error)")
}
}
...在所有内容的结尾处,我们使用重新获取顺序,
private func fetch() {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
let context = appDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "CoreDataBaseName")
let sortDescriptor = NSSortDescriptor(key: "sortOrder", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
do {
itemsArray = try context.fetch(fetchRequest)
} catch let error as NSError {
print("Could not fetch Core Data entities: \(error)")
}
}
您可以通过一百万种不同的方式来改善这个想法(这总是很受欢迎的,但这是解决方案的教学示例。
我希望它可以帮助某个人!