I have an application that first loads some data into an UIManagedDocument, then executes saveToURL:forSaveOperation:completionHandler:. Inside the completionHandler block, it does an update of various elements of this database, and when it's done, it does another saving.
Besides that, the app has 3 buttons that reload the data, re-update the data, and delete one entity of the database, respectively. In every button method, the last instruction is a saving as well.
When I run all this in the simulator, all goes smoothly. But in the device doesn't. It constantly crashes. I have observed that, normally, it crashes when pressing the "delete" button, or when reloading or re-updating the database. And it's always in the saveToURL operation.
In my opinion, the problem comes when there are multiple threads saving the database. As the device executes the code slower, maybe multiple savings come at same time and the app can't handle them correctly. Also, sometimes the delete button doesn't delete the entity, and says that doesn't exist (when it does).
I'm totally puzzled with this, and all this saving operations must be done...In fact, if I remove them, the app behaves even more incoherently.
Any suggestions of what could I do to resolve this problem? Thank you very much!
[Edit] Here I post the problematic code. For first loading the data, I use a helper class, with this two methods in particular:
+ (void)loadDataIntoDatabase:(UIManagedDocument *)database
{
[database.managedObjectContext performBlock:^{
// Read from de plist file and fill the database
[database saveToURL:database.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:^(BOOL success) {
[DataHelper completeDataOfDatabase:database];
}];
}
+ (void)completeDataOfDatabase:(UIManagedDocument *)database
{
[database.managedObjectContext performBlock:^{
// Read from another plist file and update some parameters of the already existent data (uses NSFetchRequest and works well)
// [database saveToURL:database.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:nil];
[database updateChangeCount:UIDocumentChangeDone];
}];
}
And in the view, I have 3 action methods, like these:
- (IBAction)deleteButton {
[self.database.managedObjectContext performBlock:^{
NSManagedObject *results = ;// The item to delete
[self.database.managedObjectContext deleteObject:results];
// [self.database saveToURL:self.database.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
[self.database updateChangeCount:UIDocumentChangeDone];
}];
}
- (IBAction)reloadExtraDataButton {
[DataHelper loadDataIntoDatabase:self.database];
// [self.database saveToURL:self.database.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
[self.database updateChangeCount:UIDocumentChangeDone];
}
- (IBAction)refreshDataButton {
[DataHelper completeDataOfDatabase:self.database];
//[self.database saveToURL:self.database.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:NULL];
[self.database updateChangeCount:UIDocumentChangeDone];
}
[Edit 2] More code: First of all, the initial view executes viewDidLoad this way:
- (void)viewDidLoad{
[super viewDidLoad];
self.database = [DataHelper openDatabaseAndUseBlock:^{
[self setupFetchedResultsController];
}];
}
This is what the setupFetchedResultsController method looks like:
- (void)setupFetchedResultsController
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Some entity name"];
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)]];
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
managedObjectContext:self.database.managedObjectContext
sectionNameKeyPath:nil
cacheName:nil];
}
Each view of the app (it has tabs) has a different setupFetchedResultsController in order to show the different entities the database contains.
Now, in the helper class, this is the first class method that gets executed, via the viewDidLoad of each view:
+ (UIManagedDocument *)openDatabaseAndUseBlock:(completion_block_t)completionBlock
{
NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
url = [url URLByAppendingPathComponent:@"Database"];
UIManagedDocument *database = [[UIManagedDocument alloc] initWithFileURL:url];
if (![[NSFileManager defaultManager] fileExistsAtPath:[database.fileURL path]]) {
[database saveToURL:database.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
[self loadDataIntoDatabase:database];
completionBlock();
}];
} else if (database.documentState == UIDocumentStateClosed) {
// Existe, pero cerrado -> Abrir
[database openWithCompletionHandler:^(BOOL success) {
[self loadDataIntoDatabase:database];
completionBlock();
}];
} else if (database.documentState == UIDocumentStateNormal) {
[self loadDataIntoDatabase:database];
completionBlock();
}
return database;
}
