UIManagedDocument file being automatically deleted with saveToURL:forSaveOperation:completionHandler: - ios

Question

I'm using Core Data with UIManagedDocument for an inventory-keeping app. The problem I'm having is that the "saveToURL:..." method is actually deleting my UIManagedDocument file in the Documents directory when I save using UIDocumentSaveForOverwriting after adding an item to core data. This only happens at first launch from a new build. I created a core data/UIManagedDocument helper singleton to use throughout the app.
Here's how I initialize the UIManagedDocument instance:
#interface VDFCoreDataHelper : NSObject
#property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;
#property (strong, nonatomic) UIManagedDocument *managedDocument;
#implementation VDFCoreDataHelper
- (void)createManagedDocument
{
NSURL *docsURL = [self getDocsURL];
if (![[NSFileManager defaultManager] fileExistsAtPath:[docsURL path]]) {
NSLog(#"new doc made");
_managedDocument = [[UIManagedDocument alloc] initWithFileURL:docsURL];
[self saveManagedDocumentForCreation];
[self openManagedDocument];
} else {
NSLog(#"existing doc");
_managedDocument = [[UIManagedDocument alloc] initWithFileURL:docsURL];
[self openManagedDocument];
}
}
CreateManagedDocument is called in the init method.
I have two save methods. One for creating and one for overwriting. The first one is called when I created the managed document.
At this point, I've only saved once and a UIManagedDocument directory and persistent store files exist in my documents folder.
When I want to insert an Item object (an Item entity exists), I call this method:
- (void)insertManagedObject:(NSManagedObject *)object success:(void (^)(BOOL successful))successBlock
{
NSManagedObjectContext *context = [self context];
[context insertObject:object];
NSError *error;
[context save:&error];
if (self.managedDocument.documentState == UIDocumentStateNormal) {
[self.managedDocument saveToURL:[self getDocsURL] forSaveOperation:UIDocumentSaveForOverwriting completionHandler:^(BOOL success){
successBlock(success);
}];
}
}
After "saveToURL:forSaveOperation:" for over writing is called, my managed document directory and files in my Documents folder are all automatically deleted. The managedObjectContext, Item object, and managedDocument object are all valid at this point. The document's URL points to the correct destination, but all the files are gone.
After my "insertManagedObject" method is finished, I use the navigation controller to pop back to the rootViewController which contains a table view listing the items. The data that I added are kept in memory and the fetchedResultsController loads it, but the data is not saved to disk because there isn't a persistent store any longer. When I exit the app and re-enter, nothing shows up and a new managed document is created again.
This only happens if I clear the build and launch it for the first time. If I launched and immediately exit, and then enter the app again, everything works fine. It's this "saveToURL:...: method deleting my persistent store.
I've tried subclassing UIManagedDocument and logging the errors, but it doesn't show any error whatsoever. I've tried commenting out some of the code, but they don't make a difference.
If I don't use "saveToURL", the persistent store doesn't get deleted, but upon re-launch, the fetchResultsController.fetchObjects returns an empty array and tries to access a non-existent indexPath, crashing the app.
I'm considering ditching the UIManagedDocument right about now. Hopefully, someone can tell me what I may be doing wrong, or has had the same problem.
Thanks.

Answer 1

I was struggling with the exactly same problem as you. But wasn't finding any help...
The deleting part with no error whatsoever was driving me nuts, and I almost ditched UIManagedDocument.
But I did something that actually works!.
Actually I think the problem is trying to access a document after creating it, calling to the selector:
[_document saveToURL:self.documentURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {}];
Then all I did was after saving the document I close it, get a new Instance and then reopen it. like this:
[_coreDocument saveToURL:self.documentURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
if (success) {
NSLog(#"Document created");
[_coreDocument closeWithCompletionHandler:^(BOOL success) {
if (success) {
NSLog(#"Closed recently created document, will open it again");
_coreDocument = nil;
_coreDocument = [[CheckinManagedDocument alloc] initWithFileURL:self.documentURL];
[_coreDocument openWithCompletionHandler:^(BOOL success) {
NSLog(#"Document oppened afer creating and closing it");
[self documentIsReadyForUse];
}];
}
}];
} else {
NSLog(#"Could not save the document at path: %#", self.documentURL.path);
}
}];