Map/State/Persistence.swift


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import CoreData

struct PersistenceController {
  static let shared = PersistenceController()

  static var preview: PersistenceController = {
    let result = PersistenceController(inMemory: true)
    let viewContext = result.container.viewContext
    for _ in 0..<10 {
      let newMap = Map(context: viewContext)
      newMap.uuid = UUID()
      newMap.createdAt = Date()
      newMap.title = "Map \(newMap.createdAt!.format())"
      newMap.content = ""
    }
    do {
      try viewContext.save()
    } catch {
      let nsError = error as NSError
      fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
    }
    return result
  }()

  let container: NSPersistentCloudKitContainer

  init(inMemory: Bool = false) {
    container = NSPersistentCloudKitContainer(name: "Map")

    container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
    container.viewContext.automaticallyMergesChangesFromParent = true

    if inMemory {
      container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
    }
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
      if let error = error as NSError? {
        fatalError("Unresolved error \(error), \(error.userInfo)")
      }
    })
  }
}