How create separate sqlite file with self model - objective-c

I have read this post Core Data with mutiple sqlite files and some else.
However not find any intelligible information about creation separated sqlite files (for example to store some data for different users). That's what I'm doing:
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (__persistentStoreCoordinator != nil)
{
return __persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:[NSString stringWithFormat:#"%#.sqlite", _userID]];
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
NSError *error = nil;
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return __persistentStoreCoordinator;
}
- (NSManagedObjectModel *)managedObjectModel {
if (__managedObjectModel != nil) {
return __managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:#"DataBase" withExtension:#"momd"];
__managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return __managedObjectModel;
}
- (NSManagedObjectContext *)managedObjectContext
{
if (__managedObjectContext != nil)
{
return __managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
{
__managedObjectContext = [[NSManagedObjectContext alloc] init];
[__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return __managedObjectContext;
}
If you change the user also changes NSPersistentStoreCoordinator and NSManagedObjectContext but NSManagedObjectModel - not (there NSFetchRequest). So how to separate core data (with self data and the "fetch requests") for different user without creating additionally entity(like user)?

Perhaps you could use multiple contexts with their own stores, but based on the same data model. In this way you could use the same entities for the different stores.

Related

NSManagedObjectContext crashing when accessed on external thread

I'm currently having a threading issue with the managedObjectContext within my application. Currently, I have a background thread running that MUST be in the background, but accesses the managedObjectContext at the same time. Another ViewController calls on the method processAllApplications shown below that then calls checkCompletedApplicationsFor24HourExpiration which then calls getAppsWithStatus. The thread seems to be currently locked causing this operation to halt where the warning below is. I need a way to process this through and am quite a noob when it comes to Core Data. Would anyone be able to advise. I was reading that I may have to create multiple instances of my managedObject and merge them. How would I go about that if that is the case?
AppDelegate:
- (NSManagedObjectContext *)managedObjectContext
{
[__managedObjectContext lock];
if (__managedObjectContext != nil) {
[__managedObjectContext unlock];
return __managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
__managedObjectContext = [[NSManagedObjectContext alloc] init];
[__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
[__managedObjectContext unlock];
return __managedObjectContext;
}
- (NSMutableArray*)getAppsWithStatus:(int)intStatus {
NSLog(#"%i on main thread getAppsWithStatus", [NSThread currentThread].isMainThread);
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:#"Application" inManagedObjectContext:self.managedObjectContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];
// Set example predicate and sort orderings...
NSNumber *status = [NSNumber numberWithInt:intStatus];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"status = %# && username = %#", status, [[NSUserDefaults standardUserDefaults] objectForKey:#"username"]];
#warning FAILS HERE INTO ABYSS
[request setPredicate:predicate];
NSError *error = nil;
NSMutableArray* applications = [[NSMutableArray alloc] initWithArray:[self.managedObjectContext executeFetchRequest:request error:&error]];
for (Application* eachApp in applications)
eachApp.applicationNumber = nil;
[self saveDB];
return applications;
}
- (void)processAllApplications:(id)userInfo {
[self.processApplicationsLock lock];
if ([[NSUserDefaults standardUserDefaults] objectForKey:#"username"] == nil) return; // Not logged in
NSLog(#"processing");
[self checkCompletedApplicationsFor24HourExpiration];
[self alertFor12HourCompletedApplications];
[self alertForExpiredDraftApplications];
if ([DeleteAllDraftApplicationsForCurrentApplicationYear isSatisifiedByDate:[DateTimeFactory currentApplicationDate]]) {
[self deleteExpiredApps];
}
[self performSelector:#selector(sendApplications:) withObject:nil afterDelay:3];
[self.processApplicationsLock unlock];
}
- (void)checkCompletedApplicationsFor24HourExpiration {
NSLog(#"OutboxSender - (void)checkCompletedApplicationsFor24HourExpiration");
NSLog(#"%i on main thread checkCompletedApplicationsFor24HourExpiration", [NSThread currentThread].isMainThread);
NSArray* completedApps = [self getAppsWithStatus:STATUS_COMPLETED];
NSDate* targetDate = [self offsetDate:[DateTimeFactory currentApplicationDate] withDay:-1 withMonth:0 withHour:0];
for (Application* theApplication in completedApps) {
if ([MoveCompletedApplicationToDraftApplicationSpec isSatisfiedByApplication:theApplication cutOffDate:targetDate]) {
NSLog(#"Sending To draft with date: %#", theApplication.submittedDate);
theApplication.status = [NSNumber numberWithInt:STATUS_DRAFT];
[self deleteSignatures:theApplication];
}
}
NSString* message = [NSString stringWithFormat:#"%i completed application/s have been sent to drafts", [completedApps count]];
echo_Alert(#"", message);
[self saveDB];
}
create separate managed object context
+(NSManagedObjectContext *)getManagedObjectContext
{
NSManagedObjectContext *managedObjectContext;
#try {
NSPersistentStoreCoordinator * coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
[managedObjectContext setPersistentStoreCoordinator: coordinator];
}
}
#catch (NSException *exception) {
NSLog(#"Exception occur %#",exception);
}
return managedObjectContext;
Use this separate managed object context in your fetching method,
- (NSMutableArray*)getAppsWithStatus:(int)intStatus {
NSMutableArray * mutableObjects;
NSLog(#"%i on main thread getAppsWithStatus", [NSThread currentThread].isMainThread);
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:#"Application" inManagedObjectContext:[self getManagedObjectContext]]; // Here use separate managed object context
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];
// Set example predicate and sort orderings...
NSNumber *status = [NSNumber numberWithInt:intStatus];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"status = %# && username = %#", status, [[NSUserDefaults standardUserDefaults] objectForKey:#"username"]];
#warning FAILS HERE INTO ABYSS
[request setPredicate:predicate];
NSError *error = nil;
NSMutableArray* applications = [[NSMutableArray alloc] initWithArray:[[self getManagedObjectContext] executeFetchRequest:request error:&error]];
NSMutableArray * resultedArray = [applications mutableCopy];
NSMutableArray * objectIds = [[NSMutableArray alloc] initWithCapacity:[resultedArray count]];
for (NSManagedObject *obj in resultedArray) {
[objectIds addObject:obj.objectID];
}
mutableObjects = [[NSMutableArray alloc] initWithCapacity:[objectIds count]];
for (NSManagedObjectID * objectID in objectIds) {
NSManagedObject * obj = [self.managedObjectContext
objectWithID:objectID]; // Here use self.managedObjectContext in which you already created.
[mutableObjects addObject:obj];
}
for (Application* eachApp in mutableObjects)
eachApp.applicationNumber = nil;
[self saveDB];
return mutableObjects;
}

Table using NSFetchedResultsController starts empty when using iCloud

I have my app set up to use core data with iCloud, but when it starts, the UITableView showing the data is empty, and takes a moment to fill with data. Is there any way to get it to display the data immediately, as if it didn't have iCloud integration?
- (NSManagedObjectContext *)managedObjectContext {
if (managedObjectContext != nil) {
return managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
NSManagedObjectContext* moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
[moc performBlockAndWait:^{
[moc setPersistentStoreCoordinator: coordinator];
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(mergeChangesFrom_iCloud:) name:NSPersistentStoreDidImportUbiquitousContentChangesNotification object:coordinator];
}];
managedObjectContext = moc;
managedObjectContext.mergePolicy = [[NSMergePolicy alloc]
initWithMergeType:NSMergeByPropertyObjectTrumpMergePolicyType];
}
return managedObjectContext;
}
- (void)mergeChangesFrom_iCloud:(NSNotification *)notification {
NSLog(#"Merging in changes from iCloud...");
NSManagedObjectContext* moc = [self managedObjectContext];
[moc performBlock:^{
[moc mergeChangesFromContextDidSaveNotification:notification];
NSNotification* refreshNotification = [NSNotification notificationWithName:#"SomethingChanged"
object:self
userInfo:[notification userInfo]];
[[NSNotificationCenter defaultCenter] postNotification:refreshNotification];
}];
}
- (NSManagedObjectModel *)managedObjectModel {
if (managedObjectModel != nil) {
return managedObjectModel;
}
NSString *modelPath = [[NSBundle mainBundle] pathForResource:#"EntryDatabase" ofType:#"momd"];
NSURL *modelURL = [NSURL fileURLWithPath:modelPath];
managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if((persistentStoreCoordinator != nil)) {
return persistentStoreCoordinator;
}
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];
NSPersistentStoreCoordinator *psc = persistentStoreCoordinator;
// Set up iCloud in another thread:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// ** Note: if you adapt this code for your own use, you MUST change this variable:
NSString *iCloudEnabledAppID = #"IDRemovedFromStackOverflow";
// ** Note: if you adapt this code for your own use, you should change this variable:
NSString *dataFileName = #"CoreDataStore.sqlite";
// ** Note: For basic usage you shouldn't need to change anything else
NSString *iCloudDataDirectoryName = #"Data.nosync";
NSString *iCloudLogsDirectoryName = #"Logs";
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *storePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent:dataFileName];
NSURL *localStore = [NSURL fileURLWithPath:storePath];
NSURL *iCloud = [fileManager URLForUbiquityContainerIdentifier:nil];
if (iCloud) {
NSLog(#"iCloud is working");
NSURL *iCloudLogsPath = [NSURL fileURLWithPath:[[iCloud path] stringByAppendingPathComponent:iCloudLogsDirectoryName]];
NSLog(#"iCloudEnabledAppID = %#",iCloudEnabledAppID);
NSLog(#"dataFileName = %#", dataFileName);
NSLog(#"iCloudDataDirectoryName = %#", iCloudDataDirectoryName);
NSLog(#"iCloudLogsDirectoryName = %#", iCloudLogsDirectoryName);
NSLog(#"iCloud = %#", iCloud);
NSLog(#"iCloudLogsPath = %#", iCloudLogsPath);
if([fileManager fileExistsAtPath:[[iCloud path] stringByAppendingPathComponent:iCloudDataDirectoryName]] == NO) {
NSError *fileSystemError;
[fileManager createDirectoryAtPath:[[iCloud path] stringByAppendingPathComponent:iCloudDataDirectoryName]
withIntermediateDirectories:YES
attributes:nil
error:&fileSystemError];
if(fileSystemError != nil) {
NSLog(#"Error creating database directory %#", fileSystemError);
}
}
NSString *iCloudData = [[[iCloud path]
stringByAppendingPathComponent:iCloudDataDirectoryName]
stringByAppendingPathComponent:dataFileName];
NSLog(#"iCloudData = %#", iCloudData);
NSMutableDictionary *options = [NSMutableDictionary dictionary];
[options setObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption];
[options setObject:[NSNumber numberWithBool:YES] forKey:NSInferMappingModelAutomaticallyOption];
[options setObject:iCloudEnabledAppID forKey:NSPersistentStoreUbiquitousContentNameKey];
[options setObject:iCloudLogsPath forKey:NSPersistentStoreUbiquitousContentURLKey];
[psc lock];
[psc addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:[NSURL fileURLWithPath:iCloudData]
options:options
error:nil];
[psc unlock];
}
else {
NSLog(#"iCloud is NOT working - using a local store");
NSMutableDictionary *options = [NSMutableDictionary dictionary];
[options setObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption];
[options setObject:[NSNumber numberWithBool:YES] forKey:NSInferMappingModelAutomaticallyOption];
[psc lock];
[psc addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:localStore
options:options
error:nil];
[psc unlock];
}
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:#"SomethingChanged" object:self userInfo:nil];
});
});
return persistentStoreCoordinator;
}
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
//Set up the fetched results controller.
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Entry" inManagedObjectContext:[AppDelegate applicationDelegate].managedObjectContext];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
// Sort using the timeStamp property..
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"creationDate" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Use the sectionIdentifier property to group into sections.
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[AppDelegate applicationDelegate].managedObjectContext sectionNameKeyPath:#"sectionIdentifier" cacheName:#"Root"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
self.fetchedResultsController.delegate = self;
return _fetchedResultsController;
}
A possible solution would be to create a prepopulated .sqlite-file to your bundle, and copy it to the Documents directory just before creating the persistent store coordinator

Core Data Model path vs Store path

Previously, I have an app that uses core data. I use same store url to init NSManagedObjectModel and create NSPersistentStoreCoordinator. However, in the new app, I tried to use the same way, the model can not be created. So I have to use a model url (I found it in this forum) to be able to create NSManagedObjectModel. What is the issue?
Here is from OLD app:
- (NSString *)storeName
{
return #"ABC.storedata";
}
- (NSURL *)storeUrl
{
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:self.storeName];
return storeURL;
}
- (NSManagedObjectModel *)managedObjectModel {
if (_managedObjectModel == nil) {
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:[self storeUrl]];
}
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
NSError *error = nil;
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[self storeUrl] options:nil error:&error]) {
abort();
}
return _persistentStoreCoordinator;
}
Here is from NEW app:
- (NSString *)storeName
{
return #"DEF.sqlite";
}
- (NSURL *)storeUrl
{
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:self.storeName];
return storeURL;
}
- (NSURL *)modelUrl
{
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:#"DEF" withExtension:#"momd"];
return modelURL;
}
- (NSManagedObjectModel *)managedObjectModel {
if (_managedObjectModel == nil) {
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:[self modelUrl]];
}
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
NSError *error = nil;
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[self storeUrl] options:nil error:&error]) {
abort();
}
return _persistentStoreCoordinator;
}
You can never use the same URL for both model and persistent store because they are two very different things.
Model URL must point to the actual model resource included in your Xcode project which is a .momd file package. Persistent store is in your case a database, a .sqlite file in documents directory.
I cannot imagine how it could have worked in the past. One possibility is that since your ABC.storedata did not have a trailing .sqlite, Core Data must have added a .sqlite to it behind the scenes and DEF.storedata could have matched your model name somehow?
This is the proper way to initialize a model where you replace "Model" with the name you have in the Xcode project for model resource:
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:#"Model" withExtension:#"momd"];
model = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
As for persistent store, there are no restrictions. In most cases it should be in application documents directory though.

Error after adding a new core data model version

I added a new model version, and I set the core data model to use that new version, but I get this error when the application tries to start.
"The managed object model version used to open the persistent store is incompatible with the one that was used to create the persistent store."
I'm guessing the problem is that the current persistent store is the old version of the model. Is there a way to just delete it so it makes a new one? I don't care about saving any of that data.
You have to migrate between versions. According to Apple's docs, if the changes are simple, you can do lightweight migration.
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmLightweight.html#//apple_ref/doc/uid/TP40008426-SW1
Adding these options to the NSPersistentStoreCoordinator seemed to work.
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
[NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
NSURL *url = [applicationFilesDirectory URLByAppendingPathComponent:#"YOURAPP.storedata"];
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
if (![persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType configuration:nil URL:url options:options error:&error]) {
[[NSApplication sharedApplication] presentError:error];
[persistentStoreCoordinator release], persistentStoreCoordinator = nil;
return nil;
}
return persistentStoreCoordinator;
In answer to your question, "Is there a way to delete it so it just makes a new one ?"
Yes.
Just change the persistentStoreCoordinator getter in your App Delegate as follows:
- (NSPersistentStoreCoordinator *) persistentStoreCoordinator {
if (persistentStoreCoordinator) return persistentStoreCoordinator;
NSManagedObjectModel *mom = [self managedObjectModel];
if (!mom) {
NSAssert(NO, #"Managed object model is nil");
NSLog(#"%#:%s No model to generate a store from", [self class], (char *)_cmd);
return nil;
}
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *applicationSupportDirectory = [self applicationSupportDirectory];
NSError *error = nil;
if ( ![fileManager fileExistsAtPath:applicationSupportDirectory isDirectory:NULL] ) {
if (![fileManager createDirectoryAtPath:applicationSupportDirectory withIntermediateDirectories:NO attributes:nil error:&error]) {
NSAssert(NO, ([NSString stringWithFormat:#"Failed to create App Support directory %# : %#", applicationSupportDirectory,error]));
NSLog(#"Error creating application support directory at %# : %#",applicationSupportDirectory,error);
return nil;
}
}
NSURL *url = [NSURL fileURLWithPath: [applicationSupportDirectory stringByAppendingPathComponent: #"storedata"]];
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: mom];
if (![persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType
configuration:nil
URL:url
options:nil
error:&error]){
// EDIT: if error opening persistent store, remove it and create a new one
if([[error domain] isEqualToString:#"NSCocoaErrorDomain"] && [error code] == 134100) {
NSLog(#"Core Data model was updated. Deleting old persistent store.");
[[NSFileManager defaultManager] removeItemAtURL:url error:nil];
if (![persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType
configuration:nil
URL:url
options:nil
error:&error]){
[[NSApplication sharedApplication] presentError:error];
[persistentStoreCoordinator release], persistentStoreCoordinator = nil;
return nil;
}
} else {
[[NSApplication sharedApplication] presentError:error];
[persistentStoreCoordinator release], persistentStoreCoordinator = nil;
return nil;
}
//
}
return persistentStoreCoordinator;
}
Figure out where your app stored the document and put it in the trash.
But as a extended comment you may wish to examine the possibilities around both explicit and implicit migration in NSPersistentStoreCoordinator and the options in.
- (NSPersistentStore *)addPersistentStoreWithType:(NSString *)storeType configuration:(NSString *)configuration URL:(NSURL *)storeURL options:(NSDictionary *)options error:(NSError **)error
Depending how different the versions are you can get it to happen automagically by passing NSMigratePersistentStoresAutomaticallyOption & NSInferMappingModelAutomaticallyOption
theres also
- (NSPersistentStore *)migratePersistentStore:(NSPersistentStore *)store toURL:(NSURL *)URL options:(NSDictionary *)options withType:(NSString *)storeType error:(NSError **)error

core data database is empty test

How can I test if the core data database is empty?
I tried:
NSIndexPath *path1 = [NSIndexPath indexPathForRow:0 inSection:0];
NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:path1];
if([[managedObject valueForKey:#"date"] description]!=nil){SOMEFUNCTION}else{SOMEFUNCTION}
Thanks
you have to create a fetchrequest for each entity you use in core data. if the fetchrequest returns without results you don't have objects of this entity stored in your core data.
- (BOOL)coreDataHasEntriesForEntityName:(NSString *)entityName {
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:self.managedObjectContext];
[request setEntity:entity];
[request setFetchLimit:1];
NSError *error = nil;
NSArray *results = [self.managedObjectContext executeFetchRequest:request error:&error];
if (!results) {
LogError(#"Fetch error: %#", error);
abort();
}
if ([results count] == 0) {
return NO;
}
return YES;
}
not perfect I admit but it works
my code:
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:0];
int fufu = [sectionInfo numberOfObjects];
if(fufu!=0){DATABASE IS NOT EMPTY}else{DATABASE IS EMPTY}
if someone know something more efective pls post it
I have these two methods implemented in my appDelegate:
- (NSString *)applicationDocumentsDirectory
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
return basePath;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (persistentStoreCoordinator != nil)
return persistentStoreCoordinator;
NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: #"YourApp.sqlite"]];
NSLog(#"storeURL: %#", storeUrl);
NSError *error;
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];
NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
[NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error])
{
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be
useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
Typical reasons for an error here include:
* The persistent store is not accessible
* The schema for the persistent store is incompatible with current managed object model
Check the error message to determine what the actual problem was.
*/
}// if
return persistentStoreCoordinator;
}
The storeUrl prints the path to the sqlite database.
If you open this path with a sqlite manager, you're able to see the content of your sql database. I use this SQLite Manager to analyze sqlite databases: SQLite Manager
(You can only use this method on the simulator)