> On Feb 23, 2017, at 10:43 PM, Quincey Morris > <quinceymor...@rivergatesoftware.com> wrote: > > On Feb 23, 2017, at 18:25 , Daryle Walker <dary...@mac.com > <mailto:dary...@mac.com>> wrote: >> >>> override func save(to url: URL, ofType typeName: String, for >>> saveOperation: NSSaveOperationType, completionHandler: @escaping (Error?) >>> -> Void) { >>> // Save the message data to the store so any background contexts can >>> read the data later. >>> do { >>> try self.container.viewContext.save() >>> } catch { >>> completionHandler(error) >>> return >>> } >>> >>> // Do the usual code, possibly even use a background thread. >>> super.save(to: url, ofType: typeName, for: saveOperation, >>> completionHandler: completionHandler) >>> } >> >> I found out about this method from the Document guide docs. I have two >> questions about it. >> >> 1. Is it OK to abort your override before the call to super if your >> pre-super code gets an error? > > The catch block you’ve shown seems perfectly reasonable. Unfortunately, the > documentation says you can do anything you want before or after, but “be sure > to invoke super”, which probably makes you nervous. However, I think you can > assume it’s ok to return like that if an error preventing the save occurs. > Any other assumption seems too paranoid. > > The documentation also says that the completion handler must be invoked on > the main thread, and I doubt you can assume that this save function is itself > necessarily invoked on the main thread. IAC, it’s only one extra line to > invoke the completion handler on the main thread, so I’d do that.
I thought the entire AppKit, which includes NSDocument, runs only on the main thread. The exceptions are methods that specially state that they have a multi-threaded mode. There are two methods on NSDocument, one each for reading and writing, that enable multi-threading that you have to override to return TRUE. If enabled, the background thread for writing is created within “save(to: ofType: for: completionHandler:)” and the one for reading within “NSDocumentController.openDocument(withContentsOf: display: completionHandler:)”. — Daryle Walker Mac, Internet, and Video Game Junkie darylew AT mac DOT com _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
