ViewModel.swift

final class ViewModel: ObservableObject {
  func importProducts() {
    ProductAPI.getAll { result in
      switch result {
      case .success(let products):
        self.persistenceController.container.performBackgroundTask { context in
          context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
          let batchInsert = NSBatchInsertRequest(entityName: "Product", objects: products)
          do {
            let result = try context.execute(batchInsert) as! NSBatchInsertResult
            print(result)
          }
          catch {
            let nsError = error as NSError
            // TODO: handle errors
          }
          DispatchQueue.main.async {
            objectWillChange.send()
            // TODO: handle errors
            try? resultsController.performFetch()
          }
        }
      }
    }
  }
}