CoreData.md

CoreData

• DB is an interface to the underlying SugarRecord/CoreData stack
• Use DB.shared
• You can have other stores, use the DB(bundle:) initializer, and call initialize(storeName:) afterwards.
• Use .operation(...) and .backgroundOperation(...) as needed, it's not recommended to create your own contexts.
• If you really need to have your own MOC, call .newSave()

MOC

Adds a few useful functions, such as:

• .first(...) based on import primary key, or using your own key or sorting.
• .inContext() to switch contexts.
• .findOldItems(...) for use during import.
• .removeAll(): careful, you need to reload manually!

Importing

• Use .requestInsert(...) to auto-import.
• Wrapper can be useful for metadata (pagination).
• Importable protocol for callbacks for each item, or all items.

Example of a Wrapper for pagination:

struct PaginatedFeedItem: Wrapper, Importable {
  private enum Key {
    static let content = "content"
    static let pageNumber = "pageNumber"
    static let totalPages = "totalPages"
  }

  var content: [FeedItem] = []
  var pageNumber = 0
  var totalPages = 1

  mutating func map(_ map: Map) {
    content <- map[Key.content]
    pageNumber <- map[Key.pageNumber]
    totalPages <- map[Key.totalPages]
  }

  func inContext(_ context: NSManagedObjectContext) throws -> PaginatedFeedItem {
    var result = self
    result.content = try content.map { try context.inContext($0) }
    return result
  }

  func didImport(from json: Any, in context: ImportContext) throws {
    guard let json = json as? [String: Any],
      let data = json[Key.content] as? [Any] else { return }
    try content.didImport(from: data, in: context)
  }
}