Core Data not saving an incremented integer - ios

I'm making a SpriteKit game and I need to save the player's score using Core Data. I have a property with int value that starts off as being set to "5" and increment it x amount of times. I save it then transition to a different scene and fetch it. It shows up un-incremented with the initial value of "5".
I'm new to Core Data so forgive me if this is a stupid question, but how can I get Core Data to take the incrementation in to account? Or Is information being lost when I reference the property and how can I prevent this?
self.score = 5;
self.score++
and then save by calling this method.
AppDelegate.m
-(void) createObject {
Score *scoreEntity = (Score *)[NSEntityDescription
insertNewObjectForEntityForName:#"Score"
inManagedObjectContext:self.managedObjectContext];
SpaceshipScene *spaceshipSceneReference = [[SpaceshipScene alloc] init];
id points = [NSNumber numberWithInteger: spaceshipSceneReference.score];
scoreEntity.points = points;
scoreEntity.playerName = #"Joe";
NSError *error = nil;
// Saves the managedObjectContext
if (! [[self managedObjectContext] save:&error] ) {
NSLog(#"An error! %#", error);
}
}
This is how I call it.
SpaceshipScene.m
AppDelegate *appDelegateReference = [[AppDelegate alloc] init];
[appDelegateReference createObject];
I then fetch it in another class/scene using this method
AppDelegate.m
-(void)fetchObject {
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Score"inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Sort fetched data
NSSortDescriptor *sortByPoints = [[NSSortDescriptor alloc] initWithKey:#"points" ascending:NO];
// Put them in an array
NSArray *sortDescriptor = [[NSArray alloc] initWithObjects:sortByPoints, nil];
// Pass the array to the fetch request
[fetchRequest setSortDescriptors:sortDescriptor];
NSError *error = nil;
NSArray *fetchedObjects = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects == nil) {
NSLog(#"Problem %#", error);
}
for (Score *s in fetchedObjects) {
NSLog(#" %# %d",s.playerName, [s.points integerValue]);
}
}
This is how I call it in the final scene/class
AppDelegate *appDelegateReference = [[AppDelegate alloc] init];
[appDelegateReference fetchObject];

Hope this will work, after fetching your Score entity , simply assign new values in it don't use insert object for update any value.
[scoreEntity setPoints:[NSNumber numberWithInteger: spaceshipSceneReference.score]];
[scoreEntity setPlayerName:#"Joe"];
then Save the values:
NSError *error = nil;
// Saves the managedObjectContext
if (! [[self managedObjectContext] save:&error] ) {
NSLog(#"An error! %#", error);
}

Related

Tableview cell is reloaded multiple table cell each time when its loaded

Im making a fetch request as follows,
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSFetchRequest *request = [[NSFetchRequest alloc]initWithEntityName:#"PendingShipmentDetails"];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"PendingShipmentDetails" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
then im adding the fetched records to an array as follows within viewDidLoad method...
NSArray *result = [self.managedObjectContext executeFetchRequest:request error:&error];
if (result.count > 0) {
int i;
amountArray = [[NSMutableArray alloc] init];
statusArray = [[NSMutableArray alloc]init];
shipmentReferenceNumberArray = [[NSMutableArray alloc]init];
invoiceNumberArray = [[NSMutableArray alloc]init];
for (i = 0; i < [result count]; i++) {
pending = (NSManagedObject *)[result objectAtIndex:i];
[shipmentReferenceNumberArray addObject:[pending valueForKey:#"shipmentno"]];
[invoiceNumberArray addObject:[pending valueForKey:#"invoice_no"]];
[amountArray addObject:[pending valueForKey:#"amount"]];
[statusArray addObject: [pending valueForKey:#"status"]];
}
} else {
NSLog(#"SORRY");
}
The problem is that, since adding the objects within for loop, the table cell is being populated with same value multiple times each time when Im navigating towards it. However if im adding the elements to array, outside the for loop, only one element is being added and hence only one table cell is visible at anytime. How can I get this issue sorted?
You are going in quite wrong direction
Instead of using for loop you can use enumerateObjectsUsingBlock
[ChildList enumerateObjectsUsingBlock:^(NSDictionary *obj, NSUInteger idx, BOOL * _Nonnull stop) {
Child = (ChildListModel*)[[ObjectBuilder builder] objectFromJSON:obj className:NSStringFromClass([ChildListModel class])];
if (Child) {
[originalList addObject:Child];
}
}];
Once all the elements are added in array then reload tableView,So it will return the row count as count of the array and will populated data once for each.
+ (NSArray *)fetchCoreData
{
AppDelegate * app = [[UIApplication sharedApplication]delegate];
NSFetchRequest * fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription * entity = [NSEntityDescription entityForName:#"PendingShipmentDetails" inManagedObjectContext:app.managedObjectContext];
[fetchRequest setEntity:entity];
NSError * error;
NSArray * fetchedObjects = [app.managedObjectContext executeFetchRequest:fetchRequest error:&error];
NSLog(#"Saved Data %#", fetchedObjects);
if (fetchedObjects != nil) {
return fetchedObjects;
}else{
return nil;
}
}
Try this ... i have this method fetchCoreData in my modal class. And this works perfectly for me.
Add the fetched data to array.

Error saving data in Core Data (IOS)

My program receives the JSON data from the Web service. Next, the program stores the data in the database using Core Data. If I call the save data after adding each entry, everything works, but very slowly. Keeping 200 entries takes more than one minute.
If I execute saving only once at the end – the program throw exception.
- (void) onLoadMessages:(NSObject*)object {
NSArray *messages = (NSArray*)object;
if (messages==nil) {
[self onError:#"Message array is null"];
return;
}
NSDate *date = [NSDate date];
long now = [date timeIntervalSince1970];
Boolean update = false;
for(int i=0; i<messages.count; i++) {
NSDictionary *m = messages[i];
Message *msg = [[Message alloc]initWithDictionary:m];
if ([self UpdateMessage:msg UpdateTime:now])
update = true;
}
if (update) {
NSError *error = nil;
// Error throw here
if (![self.managedObjectContext save:&error])
[self onError2:error];
}
}
- (Boolean) UpdateMessage:(Message*) msg UpdateTime:(long)now {
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Messages" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
NSString *s = [NSString stringWithFormat:#"%ld", msg.id];
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(id=%#)", s];
[fetchRequest setPredicate:pred];
NSError *error;
NSArray *object = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
Boolean result = false;
if (object==nil)
[self onError2:error];
else {
NSManagedObject *m;
if ([object count]==0) {
// Insert new message
m = [NSEntityDescription insertNewObjectForEntityForName:#"Messages"
inManagedObjectContext:self.managedObjectContext];
[m setValue:[NSNumber numberWithLong:msg.id] forKey:#"id"];
[m setValue:[NSNumber numberWithLong:msg.agancy.id] forKey:#"agancy"];
[m setValue:msg.header forKey:#"header"];
[m setValue:msg.keywords forKey:#"keywords"];
[m setValue:[NSNumber numberWithLong:msg.indate] forKey:#"indate"];
[m setValue:[NSNumber numberWithLong:now] forKey:#"updated"];
result = true;
} else {
// Update message
m = [object objectAtIndex:0];
[m setValue:[NSNumber numberWithLong:now] forKey:#"updated"];
}
// Save the context.
// Too long execution
/*NSError *error = nil;
if (![self.managedObjectContext save:&error])
[self onError2:error];*/
}
return result;
}
Help correct the behavior of the program.
With respect,
Alexander.
P.S.
Execution takes place in the main thread.
Field "Id" for table "Messages" indexed.
I solve the problem by adding privateObjectContext!
_privateObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
And replace managedObjectContext on privateObjectContext when updating/inserting data/

How to make a conditional request with NSManagedObjectContext?

I'm new to NSManagedObjectContext. I have created an entity Link in my app, which contains a NSString *url.
At some point of my app, I need to insert a new Link in my base, so I simply do this :
Link *link = [NSEntityDescription
insertNewObjectForEntityForName:#"Link"
inManagedObjectContext:self.managedObjectContext];
link.url = myUrl;
But before doing this, I want to check if there is not already a Link in my base with the same url. And I have no idea of how to do so... what should I do?
EDIT : to retrieve data from the base I'm using this method from a tool I found on the web:
// Fetch objects with a predicate
+(NSMutableArray *)searchObjectsForEntity:(NSString*)entityName withPredicate:(NSPredicate *)predicate andSortKey:(NSString*)sortKey andSortAscending:(BOOL)sortAscending andContext:(NSManagedObjectContext *)managedObjectContext
{
// Create fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
// If a predicate was specified then use it in the request
if (predicate != nil)
[request setPredicate:predicate];
// If a sort key was passed then use it in the request
if (sortKey != nil) {
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortKey ascending:sortAscending];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
}
// Execute the fetch request
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
// If the returned array was nil then there was an error
if (mutableFetchResults == nil)
NSLog(#"Couldn't get objects for entity %#", entityName);
// Return the results
return mutableFetchResults;
}
I would like to know how to use it.
Thanks for your help.
The method you provided just searches for a NSManagedObject that matches the attributes in the NSManagedObjectContext and if one exists, it returns it.
But, what you need to implement is called the Find-or-Create pattern, which is discussed in the Core Data programming guide. Basically, you search for an object matching specific criteria and if it exists that object is returned. If that object does not exist you create it.
Core Data Programming Guide
E.g.
+ (NSString *)entityName
{
return NSStringFromClass([Link class]);
}
+ (instancetype)findUsingPredicate:(NSPredicate *)predicate withContext:(NSManagedObjectContext *)context
{
Link * entity;
// Setup the fetchRequest
NSFetchRequest * fetchRequest = [NSFetchRequest fetchRequestWithEntityName:[[self class] entityName]];
fetchRequest.predicate = predicate;
// Credit: #Martin R
[fetchRequest setFetchLimit:1];
// Execute the fetchRequest
NSError *error = nil;
NSArray * matchingLinks = [context executeFetchRequest:fetchRequest error:&error];
// MatchingLinks will only return nil if an error has occurred otherwise it will return 0
if (!matchingLinks)
{
// handle error
// Core data returns nil if an error occured
NSLog(#"%s %#", __PRETTY_FUNCTION__, [error description]);
}
else if ([matchingLinks count] <= 0)
{
// if the count <= 0, there were no matches
NSLog(#"%s Not found", __PRETTY_FUNCTION__);
} else {
// A link with a url that matches the url in the dictionary was found.
NSLog(#"%s Found", __PRETTY_FUNCTION__);
entity = [matchingLinks lastObject];
}
return entity;
}
+ (instancetype)findUsingPredicate:(NSPredicate *)predicate orCreateWithContext:(NSManagedObjectContext *)context
{
Link * entity = [[self class] findUsingPredicate:predicate withContext:context];
if (!entity) {
entity = [[self class] createWithContext:context];
}
return entity;
}
+ (isntancetype)createWithContext:(NSManagedObjectContext *)context
{
return [[self class] alloc] initWithContext:context];
}
- (instancetype)initWithContext:(NSManagedObjectContext *)context
{
Link * entity = [NSEntityDescription insertNewObjectForEntityForName:[[self class] entityName] inManagedObjectContext:context];
return entity;
}
USE CASE:
NSString * url = #"http://www.mylink.com";
NSPredicate * predicate = [NSPredicate predicateWithFormat:#"url = %#", url];
Link * link = [Link findUsingPredicate:predicate orCreateWithContext:self.managedObjectContext];
link.url = url;
You can do it like this (with your method):
AppDelegate *del = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *managedObjectContext = del.managedObjectContext;
NSString *urlString = #"YOUR URL HERE";
NSMutableArray *fetchedResults = [self searchObjectsForEntity:#"Link" withPredicate:[NSPredicate predicateWithFormat:#"url == %#", urlString] andSortKey:#"url" andSortAscending:YES andContext:managedObjectContext];
BOOL exist = NO;
if(fetchedResults.count >= 1){
exist = YES;
}

Deleting object from one to many relationship in Core Data

I currently have a problem deleting an object in a to many relationship.
My app have the following relationship:
Product <<- Cart
When the user pushes a "add to cart" button in my viewcontroller, the following code is setting the relations between the product object and the cart
+ (Cart *)addProductToCartWithProduct:(Product *)product inManagedObjectContext:(NSManagedObjectContext *)context {
Cart *cart = nil;
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:#"Cart"];
NSError *error = nil;
NSArray *carts = [context executeFetchRequest:request error:&error];
if (!carts || ([carts count] > 1)) {
// handle error
} else if (![carts count]) {
cart = [NSEntityDescription insertNewObjectForEntityForName:#"Cart" inManagedObjectContext:context];
} else { // they already have a cart started
cart = [carts lastObject];
}
/*Get Object ID to safely pass NSMangedObject between threads (A background worker thread and the main thread). */
NSManagedObjectID *retID = [product objectID];
[cart addProductsObject:(Product *)[context objectWithID:retID]];
//Inverse relationship
[(Product *) [context objectWithID:retID] setInCart:cart];
return cart;
}
This then returns a cart object, which I pass to my cart viewcontroller, and fetch the products in that relationship like so:
// Fetch request for "Product":
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:#"Product"];
// Fetch only products for the cart:
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"inCart = %#", self.cart];
[fetchRequest setPredicate:predicate];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"navn" ascending:YES];
[fetchRequest setSortDescriptors:#[sortDescriptor]];
self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:_theManagedObjectContext sectionNameKeyPath:nil cacheName:nil];
_fetchedResultsController.delegate = self;
When I then try to delete an object from the relationship like so:
-(void)RemoveFromCart:(UIButton *)sender {
NSIndexPath *ip = [NSIndexPath indexPathForRow:sender.tag inSection:0];
Product *prod = (Product *)[self.fetchedResultsController objectAtIndexPath:ip];
prod.inCart = nil;
[_cart removeProductsObject:prod];
NSLog(#"Cart %# %#", _cart.products, prod);
[self saveCurrentContext:_theManagedObjectContext];
[self loadCart];
[_orderTable reloadData];
}
The product is removed visually (gone from the tableview/screen) because inCart is set to nil, but not technically... when I log the cart object, the product object is still in the relationship, so it seems like the [_cart removeProductsObject:prod]; is not working.
And it also doesn't work the other way around, when I try to add the same product to the cart, I just have deleted (from the cart), for some reason the inverse relationship "inCart" is not set, after I have set it to "nil", when the product object is removed.
Why is this happening? and how do I fix it? :).
EDIT:
Pictures showcasing inverse relationships in Core data model editor:
Pass Cart to other viewcontroller:
[[[DataManager sharedInstance] backgroundManagedObjectContext] performBlock:^{
UITabBarController *tabBarController = self.tabBarController;
for (UINavigationController *navController in tabBarController.viewControllers) {
for (UIViewController *vc in navController.viewControllers) {
if ([vc isMemberOfClass:NSClassFromString(#"CartViewController")]){
CartViewController *cartVC = (CartViewController *) vc;
cartVC.cart = [Cart addProductToCartWithProduct:prod inManagedObjectContext: [[DataManager sharedInstance] backgroundManagedObjectContext]];
[[DataManager sharedInstance] saveBackgroundContext];
[[DataManager sharedInstance] saveMasterContext];
NSLog(#" %#", cartVC.cart);
}
}
}
}];
Save Context
-(void)saveCurrentContext:(NSManagedObjectContext *)context {
NSError *error = nil;
if (![context save:&error]) {
NSLog(#"NOT SAVED");
}
[[DataManager sharedInstance] saveBackgroundContext];
[[DataManager sharedInstance] saveMasterContext];
}
Okay, so I found a work around for this very weird problem.
Since the autogenerated accessor methods didn't work for some reason, I had to think of another way to delete the object from the relationship.
for (Product *prod in _cart.products) {
//To Very reliable to check for item by name attribute, but It works :)
if ([prod.name isEqualToString:product.name]) {
product = prod;
NSMutableSet *set = [NSMutableSet setWithSet:_cart.products];
[set removeObject:prod];
_cart.products = set;
}
}

Core Data, can't save context

I'm simply trying to save a ManagedObjectContext but while I get no errors, the fetched request returns the object with none of the saved values. Consider this simple example. You have a single object, you change a property and save it. The object is there but the property is not saved. As you can see, I want only one object, and the fetch returns this one object. BTW, the code is in a simple class, not the app delegate or a view controller.
Here is the sample code:
MyAppDelegate* delegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext* context = delegate.managedObjectContext;
NSEntityDescription *myEntityDesc = [NSEntityDescription entityForName:#"MyEntity" inManagedObjectContext:context];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:myEntityDesc];
NSError *error = nil;
NSArray *array = [context executeFetchRequest:request error:&error];
MyEntity* myEntity;
if (array == nil || [array count] < 1)
{
myEntity = [NSEntityDescription insertNewObjectForEntityForName:#"MyEntity" inManagedObjectContext:context];
}
else
{
myEntity = [array objectAtIndex:0];
}
myEntity.BoolValue = [NSNumber numberWithBool:someBoolValue];
myEntity.ID = #"Some ID";
if ([context save:&error])
{
NSLog(#"no error");
}
else
{
NSLog([NSString stringWithFormat:#"found core data error: %#", [error localizedDescription]]);
}
Here's the code used to retrieve the values later:
MyAppDelegate* delegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext* context = delegate.managedObjectContext;
NSEntityDescription *MyEntityDesc = [NSEntityDescription entityForName:#"MyEntity" inManagedObjectContext:context];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:MyEntityDesc];
NSError *error = nil;
NSArray *array = [context executeFetchRequest:request error:&error];
MyEntity* myEntity;
if (array == nil || [array count] < 1)
{
//handle error
}
else
{
myEntity = [array objectAtIndex:0];
}
return [myEntity.BoolValue boolValue];
What does your NSManagedObject subclass look like? Since the fetch is working correctly (i.e. returning the entity), I suspect something is wrong in the subclass implementation.
You should declare a #property for each of the attributes on your data model. And in the implementation file, instead of using #synthesize you need to use #dynamic. Also make sure in your xcdatamodel that the entity has its class set, as well as the name.
#interface MyEntity : NSManagedObject
#property (nonatomic, strong) NSNumber * boolValue;
#end
#implementation MyEntity
#dynamic boolValue;
#end

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