SaveContext multiple times inside performBlock - ios

Question

I have flow where I should create object save it in CoreData. But by the flow I need to update object every X seconds and update it with saving context. And because there is possibility of terminating the app in coredata should be "last updated version" of the object.
Problem is that after saving context, core data not saving anymore.
Example with double saving not working:
dispatch_semaphore_t waitTodoA = dispatch_semaphore_create(0);
NSManagedObjectContext *contextA = [CoreDataManager backgroundObjectContext];
[contextA performBlock:^{
PlaceObject* placeObject = [NSEntityDescription insertNewObjectForEntityForName:#"Places" inManagedObjectContext:contextA];
placeObject.type = #"Flat";
placeObject.timestamp = [[NSDate date] timeIntervalSince1970];
[CoreDataManager saveContext:contextA];
placeObject.address = #"Sunny beach ave. 1";
placeObject.coordinates = #"0.0,0.0";
[CoreDataManager saveContext:contextA];
dispatch_semaphore_signal(waitTodoA);
}];
dispatch_semaphore_wait(waitTodoA, dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)));

Answer 1

OK, I understand what you are trying to test now. The answer is that it works perfectly for me. I pasted the following code into the tail end of -readFromURL::: in the document subclass of my document-based Core Data app:
[self.managedObjectContext performBlock:^{
Stark* stark = [NSEntityDescription insertNewObjectForEntityForName:#"Stark_entity"
inManagedObjectContext:self.managedObjectContext];
BOOL ok ;
NSError* error = nil;
NSLog(#"Testing two saves in %#", self);
stark.name = #"David";
stark.rating = #(3);
ok = [self.managedObjectContext save:&error];
NSLog(#"First Save ok=%hhd error = %#", ok, error);
stark.url = #"http://example.com";
stark.comments = #"Did it work?";
ok = [self.managedObjectContext save:&error];
NSLog(#"Second Save ok=%hhd error = %#", ok, error);
}];
Upon running this code, the NSLogs printed:
Testing two saves in BkmxDoc 0x100d308f0 "Test.bmco"
First Save ok=1 error = (null)
Second Save ok=1 error = (null)
And, upon examining the SQLite file, I found that indeed the new object had been inserted and had all four properties values assigned by the above code.
I agree with #vadian that using the dispatch_semaphore in there is strange, although I don't see any reason it would cause saving to fail. Just to prove that, in a subsequent test I added those three lines using dispatch_semaphore, retested, and it still worked.
The most likely source of the trouble is in your use of CoreDataManager. Notice that in my code, I simply used the raw `-[NSManagedObjectContext save:].