Core Data: SQLite not being updated immediately - ios

Question

There are two Entities- Document and Page. Document has a one-to-many relationship with Page.
I save the managed object context when I add document. At this point, there are no pages in them. While debugging I found that the writer context's save method does get called and is executed without error. I close and reopen the app and I can't find the previously saved Document objects. But, if I add a page in one of the document, then, the Document object appear in the table. I use a tool to view the SQLite file but my observation is not based on what I see in the tool. Even when I debug and see the number of documents present, I get 0 back when there is no page in them.
I am guessing that the Persistent Store Coordinator is doing some kind of optimization to write in batch. Can I force it to write and update the persistent store immediately? Is there a option that I can add while calling addPersistentStoreWithType on the persistent store object?
Note: Just FYI, I use this pattern to organize the Managed Object Context(s)
Fixed the issue. Here is the update
So, I was saving the whole stack all the way up to the writer context. The bug was very silly. I was trying to save the main context on the main thread like this:
- (void)saveMainContext {
[self.mainManagedObjectContext performBlock:^{
// Ensure that the main object context is being saved on the main queue
__block NSError *error = nil;
dispatch_async(dispatch_get_main_queue(), ^{
[self.mainManagedObjectContext save:&error];
});
if(!error)
{
//Write to disk after saving on the main UI context
[self saveWriterContext];
}
}];
}
As you can see, after trying to save the main context, I save the writer context. But, the bug was that I wasn't waiting for the main context to finish saving. After fixing the bug, my code looks like this:
- (void)saveMainContext {
[self.mainManagedObjectContext performBlock:^{
// Ensure that the main object context is being saved on the main queue
dispatch_async(dispatch_get_main_queue(), ^{
NSError *error = nil;
[self.mainManagedObjectContext save:&error];
if(!error)
{
//Write to disk after saving on the main UI context
[self saveWriterContext];
}
});
}];
}
And, this fixed the issue! Very silly mistake on my part.

Answer 1

Are you making sure you are saving your entire stack? If you make a change in a private context you need to save that private context. If you make a change in the main context (from the UI) then you need to save that context. Only after all of your other contexts report NO to -hasChanges should you save the writer context (aka the master context in his design).
I suspect that is your issue.
Response to OP
Hmm. Did not know that. Thanks! So, are you suggesting that I may be well off if I do not check for "error" at all, and just check for the save's return?
What I am saying is that your save should look like this (note I also correct your unnecessary dispatch_async):
- (void)saveMainContext {
[self.mainManagedObjectContext performBlock:^{
// Ensure that the main object context is being saved on the main queue
NSError *error = nil;
if (![[self mainManagedObjectContext] save:&error]) {
NSLog("Failed to save context: %#\n%#", [error localizedDescription], [error userInfo]);
exit(1);
}
[self saveWriterContext];
}];
}
The dispatch_async will be ignored because you are already on the right queue.
The call to -save: returns a bool. If and ONLY if that returns NO do you react to the error.