Loading Core Data From Large JSON Causing App To Crash - objective-c

Question

I'm attempting to populate CoreData from a JSON file that consists of 170,000 plus dictionaries. The parsing of the json goes quick but when I start trying to add to CoreData I'm blocking the main thread for a long time and then the app eventually crashes. It crashes when calling the method [UIDocument saveToUrl:forSaveOperation:completionHandler] Here is my code. If anyone has an idea of what's causing it to crash or a more efficient way to load CoreData that would be greatly appreciated.
#property (nonatomic, strong) UIManagedDocument *wordDatabase;
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
if (!self.wordDatabase) {
NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
url = [url URLByAppendingPathComponent:#"Word Database"];
self.wordDatabase = [[UIManagedDocument alloc] initWithFileURL:url];
}
}
- (void)setWordDatabase:(UIManagedDocument *)wordDatabase
{
if (_wordDatabase != wordDatabase) {
_wordDatabase = wordDatabase;
[self useDocument];
}
}
- (void)useDocument
{
if (![[NSFileManager defaultManager] fileExistsAtPath:[self.wordDatabase.fileURL path]]) {
// does not exist on disk, so create it
[self.wordDatabase saveToURL:self.wordDatabase.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
[self setupFetchedResultsController];
[self prepopulateWordDatabaseWithDocument:self.wordDatabase];
}];
}
}
- (void)prepopulateWordDatabaseWithDocument:(UIManagedDocument *)document
{
dispatch_queue_t fetchQ = dispatch_queue_create("Word Fetcher", NULL);
dispatch_async(fetchQ, ^{
//Fetch the words from the json file
NSString *fileString = [[NSBundle mainBundle] pathForResource:#"words" ofType:#"json"];
NSString *jsonString = [[NSString alloc] initWithContentsOfFile:fileString encoding:NSUTF8StringEncoding error: NULL];
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *error;
NSArray *words = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];
[document.managedObjectContext performBlock:^{
for (NSDictionary *dictionary in words)
{
[Word wordFromDictionary:dictionary inManagedObjectContext:document.managedObjectContext];
}
[document saveToURL:document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
}];
});
dispatch_release(fetchQ);
}

Answer 1

What I ended up doing that stopped my app from crashing was allocating a new NSManagedObjectContext and peformed all my loading in the background. After saving I called my NSFetchedResultsController and the table repopulated.
- (void)prepopulateWordDatabaseWithDocument:(UIManagedDocument *)document
{
NSManagedObjectContext *backgroundContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
backgroundContext.undoManager = nil;
backgroundContext.persistentStoreCoordinator = document.managedObjectContext.persistentStoreCoordinator;
[backgroundContext performBlock:^{
NSString *fileString = [[NSBundle mainBundle] pathForResource:#"words" ofType:#"json"];
NSString *jsonString = [[NSString alloc] initWithContentsOfFile:fileString encoding:NSUTF8StringEncoding error: NULL];
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *parseError;
NSArray *words = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&parseError];
for (NSDictionary *dictionary in words)
{
[Word wordFromDictionary:dictionary inManagedObjectContext:backgroundContext];
}
NSError *loadError;
if ([backgroundContext save:&loadError]) {
dispatch_async(dispatch_get_main_queue(), ^{
[self setupFetchedResultsController];
});
}
}];
}