i've got a custom tableViewCell with fetched data and a basket button, how can i save them to another entity(Basket Entity) with a click to the basket in the cell?
- (IBAction)basketButton:(id)sender
{
NSManagedObjectContext *context = [app managedObjectContext];
UIButton *button = sender;
NSInteger rowInIndexPath =button.tag;
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:rowInIndexPath inSection:0];
Basket *basket = [NSEntityDescription insertNewObjectForEntityForName:#"Basket" inManagedObjectContext:context];
//missing code
NSError *error;
if (![context save:&error])
{
NSLog(#"fail : %#", [error localizedDescription]);
}
}
Screenshot of my app
my Solutions:
i forgot to tell my function the position of the Cell.
- (IBAction)basketButton:(id)sender {
NSManagedObjectContext *context = [app managedObjectContext];
UIButton *button = sender;
NSInteger rowInIndexPath =button.tag;
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:rowInIndexPath inSection:0];
Basket *basket = [NSEntityDescription insertNewObjectForEntityForName:#"Basket" inManagedObjectContext:context];
Product *product = [self.fetchedResultsController objectAtIndexPath:indexPath];
basket.productname =product.productname ;
NSError *error;
if (![context save:&error])
{
NSLog(#"fail : %#", [error localizedDescription]);
}
}
Ugh, where to start... what you ask here does not make any sense. You seem to be unfamiliar with fundamental concepts like model, view, controller, actions... There is no way to answer/solve your problem as it stands.
Try learning more about them. See answers to https://stackoverflow.com/questions/51971/can-anyone-recommend-a-complete-objc-cocoa-or-cocoa-touch-tutorial for plenty of resources to get you started.
Related
I setup a background thread with the Parent/Child model. Essentially the context save is failing.
Here is my setup. In the AppDelegate i've setup the _managedObjectContext with the NSMainQueueConcurrencyType:
- (NSManagedObjectContext *)managedObjectContext
{
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
_managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];//[[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return _managedObjectContext;
}
In my data loading class I setup the parent/child mocs here to perform the work on the background thread:
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{
NSManagedObjectContext *mainMOC = self.managedObjectContext;
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
[moc setParentContext:mainMOC];
[moc setUndoManager:nil];
When the json data has completed I attempt to peform a save operation with the following macro:
#define SAVE_MOC { NSError *error; \
if (![moc save:&error]) { NSLog(#"Sub MOC Error"); } \
[mainMOC performBlock:^{ NSError *e = nil; if (![mainMOC save:&e]) {
NSLog(#"Main MOC Error %#",error.localizedDescription);}}];}
Also when i've completed the data load I jump back on the main thread like this:
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(#"<---- complete CS sub moc! ---->");
//this fires ok
});
So, from my SAVE_MOC macro i just get a simple error:
Main MOC Error (null)
Let me know if I can provide more info. I'm very new to multi-threading and trying to get a better handle on this approach.
Thanks,
Josh
In my data loading class I setup the parent/child mocs here to perform
the work on the background thread:
dispatch_queue_t queue =
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{
NSManagedObjectContext *mainMOC = self.managedObjectContext;
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
You should not do that. Do this instead.
NSManagedObjectContext *mainMOC = self.managedObjectContext;
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
Make sure you access the MOC in a performBlock. For example,
[moc performBlock:^{
// Anything at all involving this MOC or any of its objects
}];
When the json data has completed I attempt to peform a save operation
with the following macro:
Consider saving with something like this. Your completion block will be called when the save has finished.
- (void)saveMOC:(NSManagedObjectContext*)moc
completion:(void(^)(NSError *error))completion {
[moc performBlock:^{
NSError *error = nil;
if ([moc save:&error]) {
if (moc.parentContext) {
return [self saveMOC:moc.parentContext completion:completion];
}
}
if (completion) {
dispatch_async(dispatch_get_main_queue(), ^{
completion(error);
});
}
}];
}
[self saveMOC:moc completion:^(NSError *error) {
// Completion handler is called from main-thread, after save has finished
if (error) {
// Handle error
} else {
}
}];
EDIT
This code will crash if moc.parentContext is main concurrency type. –
Mundi
There is no inherent reason that the code I posted should cause a crash with a parent MOC of NSMainQueueConcurrencyType. It has supported being a parent context ever since parent/child was added to Core Data.
Maybe I was missing a typo, so I copy/paste saveMOC:completion: straight from this answer, and wrote the following test helper.
- (void)testWithChildConcurrencyType:(NSManagedObjectContextConcurrencyType)childConcurrencyType
parentConcurrencyType:(NSManagedObjectContextConcurrencyType)parentConcurrencyType {
NSAttributeDescription *attr = [[NSAttributeDescription alloc] init];
attr.name = #"attribute";
attr.attributeType = NSStringAttributeType;
NSEntityDescription *entity = [[NSEntityDescription alloc] init];
entity.name = #"Entity";
entity.properties = #[attr];
NSManagedObjectModel *model = [[NSManagedObjectModel alloc] init];
model.entities = #[entity];
NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
[psc addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:NULL];
NSManagedObjectContext *parent = [[NSManagedObjectContext alloc] initWithConcurrencyType:parentConcurrencyType];
parent.persistentStoreCoordinator = psc;
NSManagedObjectContext *child = [[NSManagedObjectContext alloc] initWithConcurrencyType:childConcurrencyType];
child.parentContext = parent;
NSManagedObject *obj = [NSEntityDescription insertNewObjectForEntityForName:#"Entity" inManagedObjectContext:child];
[obj setValue:#"value" forKey:#"attribute"];
XCTestExpectation *expectation = [self expectationWithDescription:[NSString stringWithFormat:#"save from %# to %# finished", concurrencyTypeString(childConcurrencyType), concurrencyTypeString(parentConcurrencyType)]];
[self saveMOC:child completion:^(NSError *error) {
// Verify data saved all the way to the PSC
NSManagedObjectContext *localMoc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
localMoc.persistentStoreCoordinator = psc;
NSFetchRequest *fr = [NSFetchRequest fetchRequestWithEntityName:#"Entity"];
XCTAssertEqualObjects(#"value", [[[localMoc executeFetchRequest:fr error:NULL] firstObject] valueForKey:#"attribute"]);
[expectation fulfill];
}];
[self waitForExpectationsWithTimeout:10 handler:nil];
}
And then, I wrote a test for each possible parent/child relationship.
- (void)testThatDoingRecursiveSaveFromPrivateToPrivateWorks {
[self testWithChildConcurrencyType:NSPrivateQueueConcurrencyType
parentConcurrencyType:NSPrivateQueueConcurrencyType];
}
- (void)testThatDoingRecursiveSaveFromPrivateToMainWorks {
[self testWithChildConcurrencyType:NSPrivateQueueConcurrencyType
parentConcurrencyType:NSMainQueueConcurrencyType];
}
- (void)testThatDoingRecursiveSaveFromMainToPrivateWorks {
[self testWithChildConcurrencyType:NSMainQueueConcurrencyType
parentConcurrencyType:NSPrivateQueueConcurrencyType];
}
- (void)testThatDoingRecursiveSaveFromMainToMainWorks {
[self testWithChildConcurrencyType:NSMainQueueConcurrencyType
parentConcurrencyType:NSMainQueueConcurrencyType];
}
So, what am I missing?
As I write this, I am reminded of a 360iDev presentation where the presenter said that you can't call performBlock on a NSMainQueueConcurrencyType context. At the time, I thought he just misspoke, meaning confinement, but maybe there is some confusion in the community about this.
You can't call performBlock on a NSConfinementConcurrencyType MOC, but performBlock is fully supported for NSMainQueueConcurrencyType.
I want to add my imageArray into coredata as transformable but this is not storing properly.
My save button coding.
- (IBAction)saveButton:(id)sender {
NSManagedObjectContext *context = [self managedObjectContext];
NSManagedObject *newEntry = [NSEntityDescription insertNewObjectForEntityForName:#"FoodInfo" inManagedObjectContext:context];
NSAttributeDescription *messageType = [[NSAttributeDescription alloc] init];
[messageType setName:#"photos"];
[messageType setAttributeType:NSTransformableAttributeType];
[imagesForShow addObject:messageType];
NSError *error = nil;
if (![context save:&error]) {
NSLog(#"Unable to save context for class" );
} else {
NSLog(#"saved all records!");
[context save:nil];
}
//[newEntry setValue:imagesForShow forKey:#"images"];
}
Here 'imagesForShow' is my array of images.
When iam going to fetch this image array , this showing nil
- (void)viewDidLoad {
[super viewDidLoad];
NSManagedObjectContext *context = [self managedObjectContext];
NSFetchRequest *request = [[NSFetchRequest alloc]initWithEntityName:#"FoodInfo"];
[request setReturnsObjectsAsFaults:NO];
arrayForPhotos = [[NSMutableArray alloc]initWithArray:[context executeFetchRequest:request error:nil]];
// Do any additional setup after loading the view.
}
What I am doing wrong with this code. Thanks.
In your save code:
NSManagedObjectContext *context = [self managedObjectContext];
NSManagedObject *newEntry = [NSEntityDescription
insertNewObjectForEntityForName:#"FoodInfo"
inManagedObjectContext:context];
NSAttributeDescription *messageType = [[NSAttributeDescription alloc] init];
[messageType setName:#"photos"];
[messageType setAttributeType:NSTransformableAttributeType];
[imagesForShow addObject:messageType];
I can't even figure out what this is supposed to do. It's completely wrong. You should never be allocating an instance of NSAttributeDescription unless you are constructing a Core Data model on the fly-- which you are not doing and which almost nobody ever does. Creating the new entry is OK. The rest, I don't know. You said that imagesForShow is your array of images, so I don't know why you're also adding an attribute description to the array.
In a more general sense, if newEntry has a transformable attribute named photos and imagesForShow is an NSArray of UIImage objects, then you could do this:
[newEntry setValue:imagesForShow forKey:#"photos"];
This is similar to a line that you have commented out, though it's not clear why it's commented out.
But whatever you do get rid of the code creating the NSAttributeDescription.
I have a routine that fetches RSS entries in the background and insert these in my NSManagedObjectContext if not already there.
My problem is that this object doesn't find duplicates or crashes, depending on which NSManagedObjectContext I use... Help me, please.
Here's the simplified .h
#interface AsyncFetchEngine : NSObject <NSXMLParserDelegate,NSFetchedResultsControllerDelegate>
#property (strong, nonatomic) dispatch_queue_t rssParserQueue;
#property (strong, nonatomic) NSMutableArray *uRLsToFetch;
#property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;
#property (strong, nonatomic) NSManagedObjectContext *childManagedObjectContext;
#property (strong, nonatomic) NSFetchedResultsController *fetchedResultsController;
- (Boolean) isAlreadyInTheFetchQueue:(Feed *)feed;
- (void) fetchPosts:(Feed *)feed;
- (void) createPostInFeed:(Feed*)feed withTitle:(NSString *)title withContent:(NSString *)content withURL:(NSString *)url withDate:(NSDate *)date;
Now here's the init method:
Note if I set the _childManagedObjectContext's parent here, the program crashes.
-(AsyncFetchEngine *)init
{
_rssParserQueue = dispatch_queue_create("com.example.MyQueue", NULL);
_uRLsToFetch = [[NSMutableArray alloc] initWithCapacity:32];
_childManagedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[_childManagedObjectContext setPersistentStoreCoordinator:[_managedObjectContext persistentStoreCoordinator]];
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self
selector:#selector(contextDidSave:)
name:NSManagedObjectContextDidSaveNotification
object:_childManagedObjectContext];
return self;
}
- (void)contextDidSave:(NSNotification*)notification
{
void (^mergeChanges) (void) = ^ {
[_managedObjectContext mergeChangesFromContextDidSaveNotification:notification];
};
if ([NSThread isMainThread]) {
mergeChanges();
} else {
dispatch_sync(dispatch_get_main_queue(), mergeChanges);
}
}
Fetch method:
Note: not sure which MOC to use to determine localFeed, _managedObjectContext crashes the app.
- (void) fetchPosts:(Feed *)feed
{
if (!_childManagedObjectContext.parentContext) {
[_childManagedObjectContext setParentContext:self.managedObjectContext];
}
if ([self isAlreadyInTheFetchQueue:feed]) {
NSLog(#"AsyncFetchEngine::fetchPosts> \"%#\" is already in the fetch queue", feed.name);
return;
}
[_uRLsToFetch addObject:feed];
NSURL *url=[NSURL URLWithString:feed.rss];
NSURLRequest *req = [[NSURLRequest alloc] initWithURL:url];
if (![NSURLConnection canHandleRequest:req]) {
return;
}
Feed *localFeed = ((Feed *)[_childManagedObjectContext existingObjectWithID:[feed objectID] error:nil]);
dispatch_async(_rssParserQueue, ^{
NSLog(#"AsyncFetchEngine::fetchPosts> Opening %#", feed.rss);
[RSSParser parseRSSFeedForRequest:req success:^(NSArray *feedItems)
{
for(RSSItem *i in feedItems)
{
[self createPostInFeed:localFeed withTitle:i.title withContent:(i.content?i.content:i.itemDescription) withURL:[i.link absoluteString] withDate:(i.pubDate?i.pubDate:[NSDate date])];
}
NSLog(#"AsyncFetchEngine::fetchPosts> Found %d items", [feedItems count]);
[_uRLsToFetch removeObject:feed];
}
failure:^(NSError *error)
{
NSLog(#"AsyncFetchEngine::fetchPosts> RSSParser lost it: %#", [error localizedDescription]);
}];
});
}
- (Boolean) isAlreadyInTheFetchQueue:(Feed *)feed
{
Feed *f=nil;
for (f in _uRLsToFetch) {
if ([f isEqual:feed]){
return YES;
}
}
return NO;
}
NSFecthedResultsController, do I need it that way?
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
// Note: I originally tried to use the main MOC here, but it also used to crash the app.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Post" inManagedObjectContext:_childManagedObjectContext];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"date" ascending:NO];
NSArray *sortDescriptors = #[sortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
/* NSPredicate *predicate =[NSPredicate predicateWithFormat:#"feed.rss LIKE '%#'", _detailItem.rss];
[fetchRequest setPredicate:predicate]; */
// Edit the section name key path and cache name if appropriate.
// nil for section name key path means "no sections".
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
aFetchedResultsController.delegate = self;
_fetchedResultsController = aFetchedResultsController;
return _fetchedResultsController;
}
It usually crashes somewhere in this method, according to the dump stack.
If it doesn't crash, I have my post added to a (null) Category...
- (void)createPostInFeed:(Feed*)feed withTitle:(NSString *)title withContent:(NSString *)content withURL:(NSString *)url withDate:(NSDate *)date
{
[_childManagedObjectContext performBlockAndWait:^{
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(#"Error in refetch: %#",[error localizedDescription]);
abort();
}
}];
NSLog(#"AsyncFetchEngine.h: Searching similar posts among %d", [[self.fetchedResultsController fetchedObjects] count]);
Boolean found=NO;
NSPredicate *predicate=[NSPredicate predicateWithFormat:#"title == %# AND url == %# AND feed == %#", title, url, feed];
NSArray *similarPosts = [_fetchedResultsController.fetchedObjects filteredArrayUsingPredicate:predicate];
if ([similarPosts count] > 0)
{
NSLog(#"\n\n\n\t\tAsyncFetchEngine::fetchPosts> Skipping %# (%#)", title, url);
} else {
NSLog(#"\n\n\n\t\tAsyncFetchEngine::fetchPosts> Putting new post in %#", feed.name);
NSEntityDescription *postEntityDescription = [NSEntityDescription entityForName:#"Post"
inManagedObjectContext:_childManagedObjectContext];
[_childManagedObjectContext performBlock:^{
Post *initPost = (Post *)[[NSManagedObject alloc]
initWithEntity:postEntityDescription
insertIntoManagedObjectContext:_childManagedObjectContext];
initPost.title = title;
initPost.url = url;
initPost.excerpt = content;
initPost.date = date;
initPost.read = nil;
initPost.feed = feed;
NSError *error;
if (![_childManagedObjectContext save:&error])
{
NSLog(#"[createPost] Error saving context: %#", error);
}
NSLog(#"Created: %# (%#)", title, url);
//[[NSNotificationCenter defaultCenter] postNotificationName:#"NewPostAdded" object:self];
}];
}
}
So, my questions are:
When I have multiple MOCs, do I fetch from the main and write to a child?
How should I respectivelly use these above?
Thanks!
Answering my own question for the sake of eventually helping another newbie.
Check NSOperationQueue with Coredata.
There's a very good example here.
I have two Entities in my CoreData model, "Valla" and "Dagbok", these are related with a many-to-many relationship.
When i add a new post to the Dagbok-entity i want it to relate to posts from Valla-entity that i store in an NSArray from a FetchRequest.
The code right now just adds a post to Dagbok
- (void)initDagbokDBWithText:(NSString *)text header:(NSString *)header degree:(int)degree weather:(NSString *)weather farg:(NSString *)farg
{
AppDelegate *appdelegate = [[UIApplication sharedApplication]delegate];
context = [appdelegate managedObjectContext];
NSEntityDescription *entitydesc = [NSEntityDescription entityForName:#"Dagbok" inManagedObjectContext:context];
NSManagedObject *newDagbok = [[NSManagedObject alloc] initWithEntity:entitydesc insertIntoManagedObjectContext:context];
//NSRelationshipDescription *dagbokRelation = [[NSRelationshipDescription alloc] init];
//NSRelationshipDescription *vallaRelation = [[NSRelationshipDescription alloc] init];
[newDagbok setValue:text forKey:#"text"];
[newDagbok setValue:header forKey:#"header"];
[newDagbok setValue:[NSNumber numberWithInt:degree] forKey:#"degree"];
[newDagbok setValue:weather forKey:#"weather"];
[newDagbok setValue:farg forKey:#"colorCode"];
NSError *error;
if(![context save:&error])
{
NSLog(#"Whoops : %#", [error localizedDescription]);
}
}
How do i add related objects from an array with fetchRequest results?
Life will be much easier if you create NSManagedObject sub classes to represent your entities rather than dealing with NSManagedObject directly. Do this by adding a name for your class in the model (the "class" property of the entity), e.g. for Valla set to VallaEntity. Then XCode can autogenerate these classes which will then have properties and methods to simplify your code, e.g.
DagbokEntity *newDagbok = [[NSManagedObject alloc] initWithEntity:entitydesc insertIntoManagedObjectContext:context];
newDagbok.text = text;
newDagbok.header = header;
newDagbok.degree = [NSNumber numberWithInt:degree];
newDagbok.weather = weather;
newDagbok.colorCode = farg;
[newDagbok addVallas:[NSSet setWithArray:arrayOfRelatedVallas]];
First question here and I've tried a bunch of stuff and can't figure it out.
Core Data with 2 entities with to-many relationship both ways
A<<---->>B
A entity has name as an attribute, and a relationship Bs
First Controller lists all A entities and i have a second controller to add A entities and I want to have it save a default B in its relationship.
In the prepare for segue I have this code:
if ([[segue identifier] isEqualToString:#"addAEntitySegue"]) {
AddAEntityViewController *addAEntityViewController = [segue destinationViewController];
addAEntityViewController.delegate = self;
addAEntityViewController.managedObjectContext = self.managedObjectContext;
NSManagedObjectContext *addingContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
self.addingManagedObjectContext = addingContext;
[addingManagedObjectContext setPersistentStoreCoordinator:[[fetchedResultsController managedObjectContext] persistentStoreCoordinator]];
addAEntityViewController.A = [NSEntityDescription insertNewObjectForEntityForName:#"A" inManagedObjectContext:addingContext];
UIBarButtonItem *saveButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSave
target:addAEntityViewController
action:#selector(save:)];
addAEntityViewController.navigationItem.rightBarButtonItem = saveButton;
}
In addAEntityViewController i have this to save
-(IBAction)save:(id)sender
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"B" inManagedObjectContext:self.managedObjectContext];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"name == %#",[defaults objectForKey:#"BDefault"]];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:predicate];
//Set the batch size to a suitable number
[fetchRequest setFetchBatchSize:20];
NSError *error;
self.A.name = textFieldVal;
[self.A addBObject:[[self.managedObjectContext executeFetchRequest:fetchRequest error:&error] objectAtIndex:0]];
NSLog(#"A = %#", self.A.Bs);
[self.delegate addAEntityViewController:self didFinishWithSave:YES];
}
In the addAEntityViewController everything saves correctly even the NSLog(#"A = %#", self.A.Bs); statement shows the B. But when the delegate saves in the First Controller (AEntityViewController) it only saves the A.name but not the relationship A.Bs, I can't figure out what's wrong.
Here's the delegate method:
-(void) addAEntityViewController:self didFinishWithSave:YES{
if (save) {
NSLog(#"saveworkouts");
NSError *error;
if (![addingManagedObjectContext save:&error]) {
// Update to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
}
// release the adding managed object context
self.addingManagedObjectContext = nil;
}
Like I said it saves the A entity but not the relationship to B even though the relationship to B saved correctly in the addAEntityViewController (the second View). An NSLOg of A.Bs is null.
First I believe that this line:
addAEntityViewController = self.managedObjectContext;
should be:
addAEntityViewController.managedObjectContext = self.managedObjectContext;
but that would also be wrong.
it should be getting the addingContext you created afterwards:
addAEntityViewController.managedObjectContext = addingContext;
I'm a bit surprised that your app didn't crash, as you are mixing managed objects from 2 different contexts.