Paul Hegarty は、授業の後、CoreData データベースを SAVE するための呼び出しを含む、彼のコードの更新バージョンを公開しました。これが、CoreData 情報が保持されない理由である可能性があります。
彼の更新メモは次のとおりです。
// should probably saveToURL:forSaveOperation:(UIDocumentSaveForOverwriting)completionHandler: here!
// we could decide to rely on UIManagedDocument's autosaving, but explicit saving would be better
// because if we quit the app before autosave happens, then it'll come up blank next time we run
// this is what it would look like (ADDED AFTER LECTURE) ...
[document saveToURL:document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
したがって、次のように「fetchFlickrDataInDocument」関数に「document saveToURL」行を追加する必要があります。
- (void)fetchFlickrDataIntoDocument:(UIManagedDocument *)document
{
dispatch_queue_t fetchQ = dispatch_queue_create("Flickr fetcher", NULL);
dispatch_async(fetchQ, ^{
NSArray *photos = [FlickrFetcher recentGeoreferencedPhotos];
[document.managedObjectContext performBlock:^{
// perform in the NSMOC's safe thread (main thread)
for (NSDictionary *flickrInfo in photos) {
[Photo photoWithFlickrInfo:flickrInfo inManagedObjectContext:document.managedObjectContext];
// table will automatically update due to NSFetchedResultsController's observing of the NSMOC
}
// should probably saveToURL:forSaveOperation:(UIDocumentSaveForOverwriting)completionHandler: here!
// we could decide to rely on UIManagedDocument's autosaving, but explicit saving would be better
// because if we quit the app before autosave happens, then it'll come up blank next time we run
// this is what it would look like (ADDED AFTER LECTURE) ...
[document saveToURL:document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
// note that we don't do anything in the completion handler this time
}];
});
}