CoreData

[JohnnyDark]

基本步骤

1. 添加 Data Model file
2. 创建entity，添加properties
3. 生成类文件
4. 创建并使用 data store： NSPersistentContainer, NSManagedObjectContext
5. context对象传递，依赖注入

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保存数据

1. 创建单条数据： let location = Location(context: managedObjectContext)
2. 保存：context.save()

获取数据：NSFetchedResultsController, NSFetchRequest

lazy var fetchedResultsController: NSFetchedResultsController<Location> = {
        let fetchRequest = NSFetchRequest<Location>()
        let entity = Location.entity()
        fetchRequest.entity = entity

        let sortDescriptor1 = NSSortDescriptor(key: "date", ascending: true)
        let sortDescriptor2 = NSSortDescriptor(key: "category", ascending: true)
        fetchRequest.sortDescriptors = [sortDescriptor2, sortDescriptor1]
        fetchRequest.fetchBatchSize = 20

        let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.managedObjectContext, sectionNameKeyPath: "category", cacheName: "Locations")

        fetchedResultsController.delegate = self
        return fetchedResultsController
    }()

查看data store中的数据

data store数据操作错误定位

[JohnnyDark]

NSFetchedResultsControllerDelegate 代理方法实现

extension LocationsViewController: NSFetchedResultsControllerDelegate{
    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        print("*** controllerWillChangeContent")
        tableView.beginUpdates()
    }

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        switch type {
        case .insert:
            print("*** NSFetchedResultsChangeInsert (object)")
            tableView.insertRows(at: [newIndexPath!], with: .fade)
        case .delete:
            print("*** NSFetchedResultsChangeDelete (object)")
            tableView.deleteRows(at: [indexPath!], with: .fade)
        case .update:
            print("*** NSFetchedResultsChangeUpdate (object)")
            if let cell = tableView.cellForRow(at: indexPath!) as? LocationCell{
                let location = controller.object(at: indexPath!) as! Location
                cell.configure(for: location)
            }
        case .move:
            print("*** NSFetchedResultsChangeMove (object)")
            tableView.deleteRows(at: [indexPath!], with: .fade)
            tableView.insertRows(at: [indexPath!], with: .fade)
        @unknown default:
            fatalError("Unhandled switch case of NSFetchedResultsChangeType")
        }
    }

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
        switch type {
        case .insert:
          print("*** NSFetchedResultsChangeInsert (section)")
          tableView.insertSections(IndexSet(integer: sectionIndex), with: .fade)
        case .delete:
          print("*** NSFetchedResultsChangeDelete (section)")
          tableView.deleteSections(IndexSet(integer: sectionIndex), with: .fade)
        case .update:
          print("*** NSFetchedResultsChangeUpdate (section)")
        case .move:
          print("*** NSFetchedResultsChangeMove (section)")
        @unknown default:
            fatalError("Unhandled switch case of NSFetchedResultsChangeType")
        }
    }

    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
        print("*** controllerDidChangeContent")
        tableView.endUpdates()
    }
}