In my application, I have Category and Sub_Category entities which are having a to-many relation ship between them.
Firstly, when the App runs for the first time the relation attribute(category_subCategory) is working as shown below:
2012-04-11 04:03:39.344 SupplyTrackerApp[27031:12f03] Saved
2012-04-11 04:03:47.423 SupplyTrackerApp[27031:fb03] Category<Category: 0x6ba4e90> (entity: Category; id: 0x6e95620 <x-coredata://00E5784E-D032-41DD-BD60-B85B0BBF8E31/Category/p1> ; data: {
categoryID = 1;
categoryName = Antiques;
"category_SubCategory" = (
"0x6ebb4f0 <x-coredata://00E5784E-D032-41DD-BD60-B85B0BBF8E31/Sub_Category/p1>"
);
catetogoryDescription = "Contains a Sub categories related to Antique pieces";
})
But when I exit the app an restart the application, that relationship does exists. The output looks like this..
2012-04-11 04:05:04.455 SupplyTrackerApp[27038:fb03] In Cell for row at index path
2012-04-11 04:05:05.548 SupplyTrackerApp[27038:fb03] Category<Category: 0x6ecaca0> (entity: Category; id: 0x6eb4ab0 <x-coredata://00E5784E-D032-41DD-BD60-B85B0BBF8E31/Category/p1> ; data: {
categoryID = 1;
categoryName = Antiques;
"category_SubCategory" = "<relationship fault: 0x6ecf0a0 'category_SubCategory'>";
catetogoryDescription = "Contains a Sub categories related to Antique pieces";
})
Here is where I'm calling the create entities..
-(void) loadDataIntoDocument{
NSLog(#"In Load Data");
dispatch_queue_t fetch=dispatch_queue_create("Data Fetcher", NULL);
dispatch_async(fetch, ^{
[Sub_Category createSubCategory:context];
NSError *error;
if (![context save:&error]) {
NSLog(#"Whoops, couldn't save: %#", [error localizedDescription]);
}else {
NSLog(#"Saved");
}
});
dispatch_release(fetch);
}
So the Sub_Category+Create Category file has the following code.
+(Sub_Category *) createSubCategory:(NSManagedObjectContext *)context{
Sub_Category *subCategory=nil;
NSFetchRequest *request=[NSFetchRequest fetchRequestWithEntityName:#"Sub_Category"];
request.predicate=[NSPredicate predicateWithFormat:#"subCategoryID=%#", #"11"];
NSSortDescriptor *sortDescriptor=[NSSortDescriptor sortDescriptorWithKey:#"subCategoryName" ascending:YES];
request.sortDescriptors=[NSArray arrayWithObject:sortDescriptor];
NSError *error;
NSArray *matches=[context executeFetchRequest:request error:&error];
if (!matches||[matches count]>1) {
///errorrrrrrrrrr
} else if([matches count]==0) {
subCategory=[NSEntityDescription insertNewObjectForEntityForName:#"Sub_Category" inManagedObjectContext:context];
subCategory.subCategoryID=[NSString stringWithFormat:#"%i", 11];
subCategory.subCategoryName=#"Antiquities";
subCategory.subCategoryDescription=#"Contains several products related to antiquities";
subCategory.subCategory_Category =[Category createCategory:context];
}else {
subCategory=[matches lastObject];
}
return subCategory;
}
And then I'm calling the Category+Create Category file which has the following code.
+(Category *) createCategory:(NSManagedObjectContext *)context{
Category *category=nil;
NSFetchRequest *request=[NSFetchRequest fetchRequestWithEntityName:#"Category"];
request.predicate=[NSPredicate predicateWithFormat:#"categoryID=%#", #"1"];
NSSortDescriptor *sortDescriptor=[NSSortDescriptor sortDescriptorWithKey:#"categoryName" ascending:YES];
request.sortDescriptors=[NSArray arrayWithObject:sortDescriptor];
NSError *error;
NSArray *matches=[context executeFetchRequest:request error:&error];
if (!matches||[matches count]>1) {
///errorrrrrrrrrr
} else if([matches count]==0) {
category=[NSEntityDescription insertNewObjectForEntityForName:#"Category" inManagedObjectContext:context];
category.categoryID=[NSString stringWithFormat:#"%d",1];
category.categoryName=#"Antiques";
category.catetogoryDescription=#"Contains a Sub categories related to Antique pieces";
}else {
category=[matches lastObject];
}
return category;
}
Can anyone help me out regarding this..
I'm stuck on this from few days...
I looks like you're using dispatch_async to do the -save: in the background. This is probably violating the "thread confinement" rules for dealing with an NSManagedObject (in short, they should only be used in the thread they were created on. Same applies to any objects fetched from them).
For more information on how to do concurrency with Core Data, see this WWDC Session.
Try only using your Core Data stack (and any objects you fetch from it) from the main thread.
Related
I am at that point where I am losing hair on this so I figured I'd reach out to the great minds here who have had experience using Objective C with Threads and core data. I am having issues with managed objects inserted in on thread in a NSPrivateQueue Context being accessed from the main thread. So at a high level I am using AFNetworking to generate a thread to make requests to retrieve JSON data from a server and then insert the values into my persistent store core data. After this is done I have another thread for downloading some binary data using AFNetworking as well. I have set up 2 managed contexts for this as shown below:
(NSManagedObjectContext *)masterManagedContext {
if (_masterManagedContext != nil) {
return _masterManagedContext;
}
NSPersistentStoreCoordinator *coord = [self coordinator];
if (coord != nil) {
_masterManagedContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
_masterManagedContext.stalenessInterval = 0.0;
[_masterManagedContext performBlockAndWait:^{
[_masterManagedContext setPersistentStoreCoordinator:coord];
}];
}
return _masterManagedContext;
}
// Return the NSManagedObjectContext to be used in the background during sync
- (NSManagedObjectContext *)backgroundManagedContext {
if (_backgroundManagedContext != nil) {
return _backgroundManagedContext;
}
NSManagedObjectContext *masterContext = [self masterManagedContext];
if (masterContext != nil) {
_backgroundManagedContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
_backgroundManagedContext.stalenessInterval = 0.0;
[_backgroundManagedContext performBlockAndWait:^{
[_backgroundManagedContext setParentContext:masterContext];
}];
}
return _backgroundManagedContext;
}
As is shown above I am using a child context and the parent context. When I make I call to fetch the json data I have something like below:
AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
//Initially delete all records in table. This will change
[[Singleton sharedInstance]removeEntityObjects:className];
for (int x=0; x < [JSON count]; x++) {
NSMutableDictionary *curDict = [JSON objectAtIndex:x];
[[CoreDatam sharedinstance] insertEmployeesWithDictionary:curDict];
}else {
/* do nothing */
}
}
}
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error,id JSON) {
[delegate performSelector:#selector(didNotCompleteSync:) withObject:className];
}];
[operations addObject:operation];
}
[self.AFClient enqueueBatchOfHTTPRequestOperations:operations progressBlock:^(NSUInteger numberOfCompletedOperations, NSUInteger totalNumberOfOperations) {
NSLog(#"Currenlty downloaded table data %d of %d!",numberOfCompletedOperations,totalNumberOfOperations);
} completionBlock:^(NSArray *operations) {
if (_syncInProgress) {
[[CoreDatam sharedInstance]updateEmpForId];
[self downloadAllFiles];
}
}];
}`
for the insert function I have something like below:
insertEmployeesWithDictionary:curDict {
[[self backgroundManagedContext]performBlockAndWait:^{
Employee *emp = [NSEntityDescription insertNewObjectForEntityForName:#"Employee"
inManagedObjectContext:[self backgroundManagedContext]];
/* Issues saving null into core data based on type.*/
[emp setFirst:[dictCopy objectForKey:#"first"]];
[emp setLast:[dictCopy objectForKey:#"last"]];
NSError *error = nil;
BOOL saved;
saved = [[self backgroundManagedContext] save:&error];
if (!saved) {
NSLog(#"Whoops, couldn't save: %#", [error localizedDescription]);
}
[self saveMasterContext];
}];
}
The issue is below where I am trying to access the managed objects in the method that is in the completion block above:
updateEmpId {
[self.backgroundManagedContext performBlockAndWait:^{
NSError *error = nil;
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:#"Employee"];
[request setSortDescriptors:[NSArray arrayWithObject:
[NSSortDescriptor sortDescriptorWithKey:#"last" ascending:YES]]];
myEmps = [self.backgroundManagedContext executeFetchRequest:request error:nil];
for (Employee *moEmp in myEmps) {
[[self backgroundManagedContext]refreshObject:moEmp mergeChanges:YES];
moEmp.photo = #'default.pic';
}
NSError *saveError = nil;
if (![self.backgroundManagedContext save:&saveError]) {
NSLog(#"Whoops, couldn't save: %#", [error localizedDescription]);
}
[self saveMasterContext];
}
The issue is that I am getting very inconsistent behavior when looking at the managed objects that are modified in the main thread. Is it still necessary to pass managed objectIds when using a parent child context relation? if so how can I do so for the above example? Any help greatly appreciated.
You should pass NSManagedObjectIDs or re-fetch in the main thread context, yeah. If you pass object IDs, get the IDs from the background context after saving the new Employee objects, and use existingObjectWithID:error: in the parent context to instantiate them there. Or just re-do the fetch request from your updateEmpId code block in the masterManagedContext.
My app requires to get data from a .Net WCF service when the device is connected to WiFi.If there's a new row added on the server,it should add it to its CoreData database. I am using a NSDictionary for comparing the local objects with the remote objects. The code is:
-(void)handleGetAllCategories:(id)value
{
if([value isKindOfClass:[NSError class]])
{
NSLog(#"This is an error %#",value);
return;
}
if([value isKindOfClass:[SoapFault class]])
{
NSLog(#"this is a soap fault %#",value);
return;
}
NSMutableArray *result = (NSMutableArray*)value;
NSMutableArray *remoteObj = [[NSMutableArray alloc]init];
for (int i = 0; i < [result count]; i++)
{
EDVCategory *catObj = [[EDVCategory alloc]init];
catObj = [result objectAtIndex:i];
[remoteObj addObject:catObj];
}
NSArray *remoteIDs = [remoteObj valueForKey:#"categoryId"];
NSFetchRequest *request = [[[NSFetchRequest alloc] init]autorelease];
request.predicate = [NSPredicate predicateWithFormat:#"categoryId IN %#", remoteIDs];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Categories" inManagedObjectContext:__managedObjectContext];
[request setEntity:entity];
NSMutableArray *results = [[NSMutableArray alloc]initWithArray:[__managedObjectContext executeFetchRequest:request error:nil]];
NSArray *existingIDs = [results valueForKey:#"categoryId"];
NSDictionary *existingObjects = [NSDictionary dictionaryWithObjects:results forKeys:existingIDs];
for (NSDictionary *remoteObjectDic in remoteObj)
{
Categories *existingObject = [existingObjects objectForKey:[remoteObjectDic valueForKey:#"categoryId"]];
if (existingObject)
{
NSLog(#"object exists");
}
else
{
NSLog(#"create new local object");
// Categories *newCategory;
// newCategory = [NSEntityDescription insertNewObjectForEntityForName:#"Categories" inManagedObjectContext:__managedObjectContext];
// [newCategory setCategoryId:[NSNumber numberWithInt:[[remoteObjectDic objectForKey:#"categoryId"]intValue]]];
// [newCategory setCategoryName:[remoteObjectDic objectForKey:#"categoryName"]];
// [newCategory setDocCount:[NSNumber numberWithInt:[[remoteObjectDic objectForKey:#"docCount"]intValue]]];
// [newCategory setCategoryType:[NSNumber numberWithInt:[[remoteObjectDic objectForKey:#"categoryType"]intValue]]];
// [newCategory setSubCategoryId:[NSNumber numberWithInt:[[remoteObjectDic objectForKey:#"subCategoryId"]intValue]]];
// [__managedObjectContext insertObject:newCategory];
}
}
[my_table reloadData];
}
The problem is,I am not able to extract values from the remote object and assign it to the NSManagedObject.I have commented the code which (according to me) should save the values in new object to the managed object. Can someone please help me achieve this?
Thanks
Here is an example of a save I did in a recent project. I have somethings in wrappers so fetching a managed object and saving look a little weird on my end. Really the only major difference I see is the act of saving. Are you saving the new NSManagedObject elsewhere in the code?
dict = (NSDictionary*)data;
#try {
if (dict) {
CaretakerInfo* info = [GenericDataService makeObjectWithEntityName:NSStringFromClass([CaretakerInfo class])];
[info setName:[dict valueForKey:#"name"]];
[info setImageURL:[dict valueForKey:#"photo"]];
[info setCaretakerID:[dict valueForKey:#"id"]];
[GenericDataService save];
}
else {
theError = [Error createErrorMessage:#"No Data" Code:-42];
}
}
#catch (NSException *exception) {
//return an error if an exception
theError = [Error createErrorMessage:#"Exception Thrown While Parsing" Code:-42];
}
If not it should looks something like this...
NSError *error = nil;
[context save:&error];
If you have anymore information about what's happening when you extract or assigning data that would be helpful (error/warning/log messages).
My model has two entities Artist and Album, and Album has a Artist instance member. I used following code to pre-populate my model but only found the last Album , that is ablum3, have set up a correct association with the Artist Beatles. For album1,album2, the artist filed are nil.
There must be something wrong which I did not spot...
//create an artist
NSManagedObject *artist = [NSEntityDescription
insertNewObjectForEntityForName:#"Artist"
inManagedObjectContext:__managedObjectContext];
[artist setValue:#"Beatles" forKey:#"name"];
//populate the data
NSArray *albums = [NSArray arrayWithObjects:#"album1",#"album2",#"album3", nil];
for (NSString *title in albums){
//populate the data
NSManagedObject *album = [NSEntityDescription
insertNewObjectForEntityForName:#"Album"
inManagedObjectContext:__managedObjectContext];
[album setValue:title forKey:#"title"];
[album setValue:artist forKey:#"artist"];
}
Without no further detail, it's difficult to know what is going on. I try to understand the model on what you have written.
So, this model works for me
albums is a to-many relationships to Album. Furthermore it's optional, you can have Artist with no Album.
artist is the inverse rel for Artist. one-to-one cardinality. It's required since you cannot have an Album without an Artist.
Here the code:
- (void)populateDB
{
//create an artist
NSManagedObject *artist = [NSEntityDescription
insertNewObjectForEntityForName:#"Artist"
inManagedObjectContext:[self managedObjectContext]];
[artist setValue:#"Beatles" forKey:#"name"];
//populate the data
NSArray *albums = [NSArray arrayWithObjects:#"album1",#"album2",#"album3", nil];
for (NSString *title in albums){
//populate the data
NSManagedObject *album = [NSEntityDescription
insertNewObjectForEntityForName:#"Album"
inManagedObjectContext:[self managedObjectContext]];
[album setValue:title forKey:#"title"];
[album setValue:artist forKey:#"artist"];
}
}
After having called populatedDB, save the context calling [self saveContext]
- (void)saveContext {
NSError *error = nil;
NSManagedObjectContext *moc = [self managedObjectContext];
if (moc != nil) {
if ([moc hasChanges] && ![moc save:&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.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
}
If you need to arrange your model let me know.
Hope that helps.
I am first time asking question here, sorry, but I can not find similar one.
So, I need update data in Entity "City" attribute - #"name".
for Example in my Core Data I already have #"New York", #"Boston".
And by parsing XML I have NSMutableArray *Cities = (#"New York", #"Boston", #"Los Angeles", #"Washington");
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
NSString *attributeString = #"name";
NSManagedObject *object = [self.fetchedResultsController objectAtIndexPath:indexPath];
//save to the TableView
cell.textLabel.text = [[object valueForKey:attributeString] description];
if ((indexPath.row + 1) == numberOfSectionsInTableView && (self.isParsingDone))
[self.insertNewObjectToCities:nil];
//When coredata updating - tableView is also updating automatically
//Here is just adding new data, but I do not know how to update
- (void)insertNewObjectToCities_translation:(id)sender
{
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];
NSString *attributeString = #"name";
if (![[self.parseCities.Cities objectAtIndex:i] isEqualToString:[newManagedObject valueForKey:attributeString]])
{
[newManagedObject setValue:[self.parseCities.Cities objectAtIndex:i] forKey:attributeString];
NSLog(#"OBBB %#", [self.parseCities.Cities objectAtIndex:i]);
NSLog(#"dessss %#", [[newManagedObject valueForKey:attributeString] description]);
i++;
if (i==[self.parseCities.Cities count])
{
i = 0;
return;
}
else
{
NSLog(#"valueForKey %#", [newManagedObject valueForKey:attributeString]);
[self insertNewObjectToCities_translation:nil];
}
}
else
{
NSLog(#"else");
return;
}
// Save the context.
NSError *error = nil;
if (![context save:&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.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
To update a managed object, you first need to fetch it, make any changes to the fields in the fetched NSManagedObject, and then save the context you used to fetch the object. If you call insertNewObjectForEntityForName again, it will insert a new managed object every time, even if it already exists in Core Data.
It's quite slow to fetch a single object every time you need to check and see if a new one needs to be added. You might want to cache the objects you currently have loaded (or their unique identifying field) into an NSArray or NSSet so you can check that for membership, instead.
I read much about Core Data.. but what is an efficient way to make a count over an Entity-Type (like SQL can do with SELECT count(1) ...). Now I just solved this task with selecting all with NSFetchedResultsController and getting the count of the NSArray! I am sure this is not the best way...
I don't know whether using NSFetchedResultsController is the most efficient way to accomplish your goal (but it may be). The explicit code to get the count of entity instances is below:
// assuming NSManagedObjectContext *moc
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:entityName inManagedObjectContext:moc]];
[request setIncludesSubentities:NO]; //Omit subentities. Default is YES (i.e. include subentities)
NSError *err;
NSUInteger count = [moc countForFetchRequest:request error:&err];
if(count == NSNotFound) {
//Handle error
}
[request release];
To be clear, you aren't counting entities, but instances of a particular entity. (To literally count the entities, ask the managed object model for the count of its entities.)
To count all the instances of a given entity without fetching all the data, the use -countForFetchRequest:.
For example:
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity: [NSEntityDescription entityForName: entityName inManagedObjectContext: context]];
NSError *error = nil;
NSUInteger count = [context countForFetchRequest: request error: &error];
[request release];
return count;
Swift
It is fairly easy to get a count of the total number of instances of an entity in Core Data:
let context = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "MyEntity")
let count = context.countForFetchRequest(fetchRequest, error: nil)
I tested this in the simulator with a 400,000+ object count and the result was fairly fast (though not instantaneous).
I'll just add that to make it even more efficient... and because its just a count, you don't really need any property value and certainly like one of the code examples above you don't need sub-entities either.
So, the code should be like this:
int entityCount = 0;
NSEntityDescription *entity = [NSEntityDescription entityForName:#"YourEntity" inManagedObjectContext:_managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:entity];
[fetchRequest setIncludesPropertyValues:NO];
[fetchRequest setIncludesSubentities:NO];
NSError *error = nil;
NSUInteger count = [_managedObjectContext countForFetchRequest: fetchRequest error: &error];
if(error == nil){
entityCount = count;
}
Hope it helps.
I believe the easiest and the most efficient way to count objects is to set NSFetchRequest result type to NSCountResultType and execute it with NSManagedObjectContext countForFetchRequest:error: method.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:entityName];
fetchRequest.resultType = NSCountResultType;
NSError *fetchError = nil;
NSUInteger itemsCount = [managedObjectContext countForFetchRequest:fetchRequest error:&fetchError];
if (itemsCount == NSNotFound) {
NSLog(#"Fetch error: %#", fetchError);
}
// use itemsCount
I wrote a simple utility method for Swift 3 to fetch the count of the objects.
static func fetchCountFor(entityName: String, predicate: NSPredicate, onMoc moc: NSManagedObjectContext) -> Int {
var count: Int = 0
moc.performAndWait {
let fetchRequest: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: entityName)
fetchRequest.predicate = predicate
fetchRequest.resultType = NSFetchRequestResultType.countResultType
do {
count = try moc.count(for: fetchRequest)
} catch {
//Assert or handle exception gracefully
}
}
return count
}
It's really just this:
let kBoat = try? yourContainer.viewContext.count(for: NSFetchRequest(entityName: "Boat"))
"Boat" is just the name of the entity from your data model screen:
What is the global yourContainer?
To use core data, at some point in your app, one time only, you simply go
var yourContainer = NSPersistentContainer(name: "stuff")
where "stuff" is simply the name of the data model file.
You'd simply have a singleton for this,
import CoreData
public let core = Core.shared
public final class Core {
static let shared = Core()
var container: NSPersistentContainer!
private init() {
container = NSPersistentContainer(name: "stuff")
container.loadPersistentStores { storeDescription, error in
if let error = error { print("Error loading... \(error)") }
}
}
func saveContext() {
if container.viewContext.hasChanges {
do { try container.viewContext.save()
} catch { print("Error saving... \(error)") }
}
}
}
So from anywhere in the app
core.container
is your container,
So in practice to get the count of any entity, it's just
let k = try? core.container.viewContext.count(for: NSFetchRequest(entityName: "Boat"))
In Swift 3
static func getProductCount() -> Int {
let moc = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Product")
let count = try! moc.count(for: fetchRequest)
return count
}
If you want to find count for specific predicated fetch, i believe this is the best way:
NSError *err;
NSUInteger count = [context countForFetchRequest:fetch error:&err];
if(count > 0) {
NSLog(#"EXIST");
} else {
NSLog(#"NOT exist");
}
Swift 5 solution:
var viewContext: NSManagedObjectContext!
do {
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "insertName")
let count = try viewContext.count(for: fetchRequest)
print("Counted \(count) objects")
}
catch {
print("Error")
}