I have a textfield where users enter a username and click add.
Is this the best way to do this?:
Make query for name of user. If user does not exist, give warning message. If user does exist, add them to relations with this:
[self.friends addObject:user];
[friendsRelation addObject:user];
Another question is, how do I search for a user with a query and return an object?
Also, here are some variables I made in .h
#property (nonatomic, strong) NSArray *allUsers;
#property (nonatomic, strong) PFUser *currentUser;
#property (nonatomic, strong) NSMutableArray *friends;
#property (nonatomic, strong) PFUser *foundUser;
- (BOOL)isFriend:(PFUser *)user;
Check out the below code and you can tailor it to your more specific needs, but it generally does what you are asking for. I strongly advise you to read the documentation on all the methods in the code, and check some Parse tutorials or sample code - they have this covered extensively.
// create and set query for a user with a specific username
PFQuery *query = [PFUser query];
[query whereKey:#"username" equalTo:#"usernameYouWantToAdd"];
// perform the query to find the user asynchronously
[query getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) {
if (error) {
NSLog(#"Error: %# %#", error, [error userInfo]);
// the Parse error code for "no such user" is 101
if (error.code == 101) {
NSLog(#"No such user");
}
}
else {
// create a PFUser with the object received from the query
PFUser *user = (PFUser *)object;
[friendsRelation addObject:user];
[self.friends addObject:user];
// save the added relation in the Parse database
[self.currentUser saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
if (error) {
NSLog(#" %# %#", error, [error userInfo]);
}
}];
}
}];
Note that referencing self inside the block can lead to a retain cycle and thus a memory leak. To prevent this, you can get create a weak reference to self outside the block, where ClassOfSelf is the class of what self is, in this case most likely your view controller:
__weak ClassOfSelf *weakSelf = self;
And then use it to access self in the block, for example:
[weakSelf.friends addObject:user];
First, to add a relation I would first get the relation column from the user, addObject on that relation, then just save the user.
Next, what kind of query are you looking for? Do you want to query for the friends of a user? Query the user table for users who are friends with so and so? Could you elaborate?
Related
I'm saving a users zip code to the Firebase database and want to query that database on app launch to see if the user has input their zip code already or if they're a brand new user.
I've posted my code before. I pulled the sample code from the Firebase docs, but it seems that my app is never even running the following code to get the value
[[[_ref child:#"user"] child:userID] observeSingleEventOfType:FIRDataEventTypeValue withBlock:^(FIRDataSnapshot * _Nonnull snapshot) {...
What am I missing out on?
#import "FollowingVC.h"
#import <FirebaseDatabase/FirebaseDatabase.h>
#import Firebase;
#interface FollowingVC ()
#property NSString *uid;
#property FIRDatabaseReference *ref;
#property NSString *zipcode;
#end
#implementation FollowingVC
- (void)viewDidLoad {
[super viewDidLoad];
[self createAuthorizedUser];
[self checkForZipCode];
}
-(void)createAuthorizedUser
{
[[FIRAuth auth]
signInAnonymouslyWithCompletion:^(FIRUser *_Nullable user, NSError *_Nullable error) {
if (!error) {
self.uid = user.uid;
self.ref=[[FIRDatabase database]reference];
}
}];
}
-(void)checkForZipCode
{
NSString *userID = [FIRAuth auth].currentUser.uid;
[[[_ref child:#"user"] child:userID] observeSingleEventOfType:FIRDataEventTypeValue withBlock:^(FIRDataSnapshot * _Nonnull snapshot) {
// Get user value
self.zipcode = snapshot.value[#"zip code"];
NSLog(#"It worked: %#", self.zipcode);
// ...
} withCancelBlock:^(NSError * _Nonnull error) {
NSLog(#"%#", error.localizedDescription);
}];
}
#end
Firebase is asynronous and you need to allow time for events to complete before moving on in the app.
In this case, you should call [self checkForZipCode] inside the sign-in block after self.uid is populated.
Otherwise you run the risk of the checkForZipCode function running before the self.uid is populated.
Let Firebase control the flow of the app - and don't try to use Firebase synchronously as it will get you into trouble due to internet lag etc.
When opening a locked file using my NSPersistentDocument subclass I get the following message in the console:
Attempt to add read-only file at path [URL] read/write. Adding
it read-only instead. This will be a hard error in the future; you
must specify the NSReadOnlyPersistentStoreOption.
The document window title is '(document name) - Locked'. After the user unlocks it, makes a change and then attempts to save, the save fails with the error
An error occurred while saving.
It seems that NSPersistentDocument fails to recognize that the user has unlocked the document and doesn't reopen it in read/write mode. Is this a bug in NSPersistentDocument or am I missing something here?
I am not overriding any of the file I/O methods in NSPersistentDocument.
Ah, ok automatic file locking.
That happens for auto-save documents not accessed in a while.
The typical approach is to notice the lock before creating the core data stack and put up a dialog asking the user to unlock the file.
If they agree to unlock the file, you simply unlock it and run as normal.
If they don't agree to unlock it, you copy it or open it readonly. Of course, you could simply bypass the user's preference and automatically unlock the file anyway, but that's probably not very nice.
Here is a category that should help you determine if a file is locked, and also lock/unlock the file.
Note, that this is entirely separate from the files mode being changed to read-only, but you can handle it in a similar manner.
Category interface
#interface NSFileManager (MyFileLocking)
- (BOOL)isFileLockedAtPath:(NSString *)path;
- (BOOL)unlockFileAtPath:(NSString*)path error:(NSError**)error;
- (BOOL)lockFileAtPath:(NSString*)path error:(NSError**)error;
#end
Category implementation
#implementation NSFileManager (MyFileLocking)
- (BOOL)isFileLockedAtPath:(NSString *)path {
return [[[self attributesOfItemAtPath:path error:NULL]
objectForKey:NSFileImmutable] boolValue];
}
- (BOOL)unlockFileAtPath:(NSString*)path error:(NSError**)error {
return [self setAttributes:#{NSFileImmutable:#NO}
ofItemAtPath:path
error:error];
}
- (BOOL)lockFileAtPath:(NSString*)path error:(NSError**)error {
return [self setAttributes:#{NSFileImmutable:#YES}
ofItemAtPath:path
error:error];
}
#end
Then, you can call [[NSFileManager defaultManager] isFileLockedAtPath:path] to determine if it is locked, and if it is, throw up a dialog asking the user what to do about it. You can then unlock it and open the stack as normal, or leave it locked and open the stack read-only, which will prevent saves from changing the file store.
Note that you can also monitor the file, and know when it changes from locked/unlocked and respond accordingly.
For Apple's guidelines on this, see https://developer.apple.com/library/mac/documentation/DataManagement/Conceptual/DocBasedAppProgrammingGuideForOSX/StandardBehaviors/StandardBehaviors.html
EDIT
Ok. I would have liked for NSPersistentDocument to replicate the
behavior in NSDocument - where the prompt to unlock comes only when an
edit is attempted. What you're saying is that there is no such feature
in NSPersistentDocument? – Aderstedt
OK. I thought you were wanting to ask the user to unlock it so that it could be opened read/write.
If you want to "go with the flow" and open it read-only when necessary, then you should add a little customization to your NSPersistentDocument subclass.
First, you want to add a little state to keep track of whether or not the original options specified a read-only file.
#implementation MyDocument {
BOOL explicitReadOnly;
}
Then, you will want a couple of utility methods...
- (NSDictionary*)addReadOnlyOption:(NSDictionary*)options {
NSMutableDictionary *mutable = options ? [options mutableCopy]
: [NSMutableDictionary dictionary];
mutable[NSReadOnlyPersistentStoreOption] = #YES;
return [mutable copy];
}
- (NSDictionary*)removeReadOnlyOption:(NSDictionary*)options {
NSMutableDictionary *mutable = options ? [options mutableCopy]
: [NSMutableDictionary dictionary];
[mutable removeObjectForKey:NSReadOnlyPersistentStoreOption];
return [mutable copy];
}
Next, you want to provide your own persistent store coordinator configuration code. This allows you to provide the read-only option to the store when you create it. This method is automatically called when you build your document, all you need to do is provide an override implementation.
- (BOOL)configurePersistentStoreCoordinatorForURL:(NSURL *)url
ofType:(NSString *)fileType
modelConfiguration:(NSString *)configuration
storeOptions:(NSDictionary<NSString *,id> *)storeOptions
error:(NSError * _Nullable __autoreleasing *)error {
explicitReadOnly = [storeOptions[NSReadOnlyPersistentStoreOption] boolValue];
if (![[NSFileManager defaultManager] isWritableFileAtPath:url.path]) {
storeOptions = [self addReadOnlyOption:storeOptions];
}
return [super configurePersistentStoreCoordinatorForURL:url
ofType:fileType
modelConfiguration:configuration
storeOptions:storeOptions
error:error];
}
Also, notice that NSPersistentDocument implements the NSFilePresenter protocol. Thus, you can override a method and be notified whenever the file content or attributes are changed. This will notify you for any change to the file, including lock/unlock from within your application, the Finder, or any other mechanism.
- (void)presentedItemDidChange {
[self ensureReadOnlyConsistency];
[super presentedItemDidChange];
}
We then want to ensure that our persistent store remains consistent with the read-only properties of the file.
Here is one implementation, that just changes the store's readOnly property.
- (void)ensureReadOnlyConsistency {
NSURL *url = [self presentedItemURL];
BOOL fileIsReadOnly = ![[NSFileManager defaultManager] isWritableFileAtPath:url.path];
NSPersistentStoreCoordinator *psc = self.managedObjectContext.persistentStoreCoordinator;
[psc performBlock:^{
NSPersistentStore *store = [psc persistentStoreForURL:url];
if (store) {
if (fileIsReadOnly) {
if (!store.isReadOnly) {
store.readOnly = YES;
}
} else if (!explicitReadOnly) {
if (store.isReadOnly) {
store.readOnly = NO;
}
}
}
}];
}
This works, but has one little hangup. If the store is originally opened with read-only options, then the very first time the readOnly attribute is set to NO, that first save throws (actually, it's the obtainPermanentIDsForObjects:error: call. Core data appears to catch the exception, but it is logged to the console.
The save continues, and nothing seems amiss. All the objects get saved, and the object IDs are properly obtained and recorded as well.
So, there is nothing that does not work that I can tell.
However, there is another more draconian option, but it avoids the aforementioned "issue." You can replace the store.
- (void)ensureReadOnlyConsistency {
NSURL *url = [self presentedItemURL];
BOOL fileIsReadOnly = ![[NSFileManager defaultManager] isWritableFileAtPath:url.path];
NSPersistentStoreCoordinator *psc = self.managedObjectContext.persistentStoreCoordinator;
[psc performBlock:^{
NSPersistentStore *store = [psc persistentStoreForURL:url];
if (store) {
if (fileIsReadOnly != store.isReadOnly) {
NSString *type = store.type;
NSString *configuration = store.configurationName;
NSDictionary *options = store.options;
if (fileIsReadOnly) {
options = [self addReadOnlyOption:options];
} else if (!explicitReadOnly) {
options = [self removeReadOnlyOption:options];
}
NSError *error;
if (![psc removePersistentStore:store error:&error] ||
![psc addPersistentStoreWithType:type
configuration:configuration
URL:url
options:options
error:&error]) {
// Handle the error
}
}
}
}];
}
Finally, note that the notification happens when the operating system notices that the file has changed. When the file is locked/unlocked from within your application, you can get a faster notification.
You can override these two methods to get a little quicker response to the change...
- (void)lockWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler {
[super lockWithCompletionHandler:^(NSError * _Nullable error) {
if (completionHandler) completionHandler(error);
if (!error) [self ensureReadOnlyConsistency];
}];
}
- (void)unlockWithCompletionHandler:(void (^)(NSError * _Nullable))completionHandler {
[super unlockWithCompletionHandler:^(NSError * _Nullable error) {
if (completionHandler) completionHandler(error);
if (!error) [self ensureReadOnlyConsistency];
}];
}
I hope that's what you are looking for.
I am using CoreData with MagicalRecord.
I'd like to insert Data in following code, but to insert data become an error with a message Cocoa error 133000.
AppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
[MagicalRecord setupCoreDataStackWithAutoMigratingSqliteStoreNamed:#"class_schedule.sqlite"];
return YES;
}
ViewController.m
- (void)saveData
{
Data *data = [Data MR_createEntity];
[MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {
Data *localData = [data MR_inContext:localContext];
localData.title = textField.text;
} completion:^(BOOL success, NSError *error) {
}];
}
Data.h
#interface Data : NSManagedObject
#property (nonatomic, retain) NSNumber * id;
#property (nonatomic, retain) NSString * title;
#end
Can you tell me how to insert record with Magical Record?
Error:
Cocoa error 133000 is:
NSManagedObjectReferentialIntegrityError = 133000, // attempt to fire a fault pointing to an object that does not exist (we can see the store, we can't see the object)
(Taken from this SO question). Basically you are doing something with a NSManagedObject that doesn't exist.
Inserting data:
In terms of how to insert data using magical record take a look at this tutorial which will probably explain it much better than I can.
My advice:
Use Core Data straight up. It's quite a steep learning curve, but very quickly becomes intuitive and easy to use. It will also stand you in good stead if you know how it all works rather than relying on a third party.
If you're interested in how it works at a more fundamental level, take a look at SQLite. I wouldn't necessarily recommend using it as it is a C library but it will help you get a deeper understanding.
You get error 133000 when you try to access object that is not existing. "But hey", you might say, "what do you mean not existing? I'm creating it right there!".
When you are creating NSManagedObject like you do, that is with MR_createEntity, under the hood it calls
NSManagedObject *newEntity = [self MR_createEntityInContext:[NSManagedObjectContext MR_contextForCurrentThread]]
This context is not saved in any way by doing that, and created entity is not persisted. Then by calling
Data *localData = [data MR_inContext:localContext];
You are actually making this under the hood:
BOOL success = [[self managedObjectContext] obtainPermanentIDsForObjects:#[self] error:&error];
The problem is that if NSManagedObject isn't persisted, you won't get persistent ID that is next used in
NSManagedObject *inContext = [otherContext existingObjectWithID:[self objectID] error:&error];
Above method fails to retrieve existing object because it's not existing in store yet (remember, context for current thread in which created entity exists is not saved at any point).
But worry not, fix for this is pretty simple. Don't create new entity like that. Instead do it like this:
[MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {
Data *localData = [data MR_createEntityInContext:localContext];
localData.title = textField.text;
} completion:^(BOOL success, NSError *error) {
}];
That way create entity and modify in context that is going to be saved immediately. This is the correct way to create entities in MagicalRecord.
I am new to ObjC and I am struggling with the CLGeocoder. I want to be able to use reverseGeocodeLocation to obtain a string that contains the user location that I pass to my delegate when the user presses a Done button.
So the user triggers the display of a MapViewController, I call the reverseGeocodeLocation in the viewDidLoad but the [placemarks count = 0] this first time in, and I have no placemark to get the info that I need. The second time the user triggers the display of the MapViewController the placemarks array has been populated and everything works.
I suspect it is something to do with the reverseGeocodeLocation being an asynchronous call - but I cannot figure out how to solve this problem. I have tried searching online but nothing seems to help me understand what I am doing wrong and how i can solve this issue. Thanks in advance.
#interface MapViewController ()
#property (strong, nonatomic) CLGeocoder *geocoder;
#property (readwrite, nonatomic) NSString *theLocationName;
#end
#implementation MapViewController
#synthesize mapView, geocoder, delegate = _delegate, theLocationName = _theLocationName;
- (void)viewDidLoad
{
[super viewDidLoad];
self.mapView.delegate=self;
self.mapView.showsUserLocation = YES;
[self theUserLocation];
}
-(void)theUserLocation
{
if (!geocoder)
{
geocoder = [[CLGeocoder alloc] init];
}
MKUserLocation *theLocation;
theLocation = [self.mapView userLocation];
[geocoder reverseGeocodeLocation:theLocation.location
completionHandler:^(NSArray* placemarks, NSError* error)
{
if ([placemarks count] > 0)
{
CLPlacemark *placemark = [placemarks objectAtIndex:0];
[self setTheLocationName: placemark.locality];
}
}];
- (IBAction)done:(id)sender
{
[[self delegate] mapViewControllerDidFinish:self locationName:[self theLocationName]];
}
#end
This is not exact answer to your question but, if you can switch to other solution apart from CLGeocoder than following function can help you to get address from given latitude, longitude
#define kGeoCodingString #"http://maps.google.com/maps/geo?q=%f,%f&output=csv" //define this at top
-(NSString *)getAddressFromLatLon:(double)pdblLatitude withLongitude:(double)pdblLongitude
{
NSString *urlString = [NSString stringWithFormat:kGeoCodingString,pdblLatitude, pdblLongitude];
NSError* error;
NSString *locationString = [NSString stringWithContentsOfURL:[NSURL URLWithString:urlString] encoding:NSASCIIStringEncoding error:&error];
locationString = [locationString stringByReplacingOccurrencesOfString:#"\"" withString:#""];
return [locationString substringFromIndex:6];
}
Credit : Selected Answer to this question
So the user triggers the display of a MapViewController, I call the reverseGeocodeLocation in the viewDidLoad but the [placemarks count = 0] this first time in, and I have no placemark to get the info that I need. The second time the user triggers the display of the MapViewController the placemarks array has been populated and everything works.
It's not because the call is asynchronous - it's because the first time you call theUserLocation the actual location isn't available. Getting the user's location is not instantaneous - it takes time. However, you're asking for the user's location as soon as the map loads, which in most circumstances won't work.
What you need to do is hook into the MKMapViewDelegate methods, which provide you with callbacks when the location is updated. You can use this to check the location's accuracy, and decide whether it is accurate enough for you to reverse geolocate.
This is my first question on Stack Overflow, so please excuse me if I'm breaking any etiquette. I'm also fairly new to Objective-C/app creation.
I have been following the CS193P Stanford course, in particular, the CoreData lectures/demos. In Paul Hegarty's Photomania app, he starts with a table view, and populates the data in the background, without any interruption to the UI flow. I have been creating an application which lists businesses in the local area (from an api that returns JSON data).
I have created the categories as per Paul's photo/photographer classes. The creation of the classes themselves is not an issue, it's where they are being created.
A simplified data structure:
- Section
- Sub-section
- business
- business
- business
- business
- business
- business
My application starts with a UIViewController with several buttons, each of which opens a tableview for the corresponding section (these all work fine, I'm trying to provide enough information so that my question makes sense). I call a helper method to create/open the URL for the UIManagedDocument, which was based on this question. This is called as soon as the application runs, and it loads up quickly.
I have a method very similar to Paul's fetchFlickrDataIntoDocument:
-(void)refreshBusinessesInDocument:(UIManagedDocument *)document
{
dispatch_queue_t refreshBusinessQ = dispatch_queue_create("Refresh Business Listing", NULL);
dispatch_async(refreshBusinessQ, ^{
// Get latest business listing
myFunctions *myFunctions = [[myFunctions alloc] init];
NSArray *businesses = [myFunctions arrayOfBusinesses];
// Run IN document's thread
[document.managedObjectContext performBlock:^{
// Loop through new businesses and insert
for (NSDictionary *businessData in businesses) {
[Business businessWithJSONInfo:businessData inManageObjectContext:document.managedObjectContext];
}
// Explicitly save the document.
[document saveToURL:document.fileURL
forSaveOperation:UIDocumentSaveForOverwriting
completionHandler:^(BOOL success){
if (!success) {
NSLog(#"Document save failed");
}
}];
NSLog(#"Inserted Businesses");
}];
});
dispatch_release(refreshBusinessQ);
}
[myFunctions arrayOfBusinesses] just parses the JSON data and returns an NSArray containing individual businessses.
I have run the code with an NSLog at the start and end of the business creation code. Each business is assigned a section, takes 0.006 seconds to create, and there are several hundred of these. The insert ends up taking about 2 seconds.
The Helper Method is here:
// The following typedef has been defined in the .h file
// typedef void (^completion_block_t)(UIManagedDocument *document);
#implementation ManagedDocumentHelper
+(void)openDocument:(NSString *)documentName UsingBlock:(completion_block_t)completionBlock
{
// Get URL for document -> "<Documents directory>/<documentName>"
NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
url = [url URLByAppendingPathComponent:documentName];
// Attempt retrieval of existing document
UIManagedDocument *doc = [managedDocumentDictionary objectForKey:documentName];
// If no UIManagedDocument, create
if (!doc)
{
// Create with document at URL
doc = [[UIManagedDocument alloc] initWithFileURL:url];
// Save in managedDocumentDictionary
[managedDocumentDictionary setObject:doc forKey:documentName];
}
// If the document exists on disk
if ([[NSFileManager defaultManager] fileExistsAtPath:[url path]])
{
[doc openWithCompletionHandler:^(BOOL success)
{
// Run completion block
completionBlock(doc);
} ];
}
else
{
// Save temporary document to documents directory
[doc saveToURL:url
forSaveOperation:UIDocumentSaveForCreating
completionHandler:^(BOOL success)
{
// Run compeltion block
completionBlock(doc);
}];
}
}
And is called in viewDidLoad:
if (!self.lgtbDatabase) {
[ManagedDocumentHelper openDocument:#"DefaultLGTBDatabase" UsingBlock:^(UIManagedDocument *document){
[self useDocument:document];
}];
}
useDocument just sets self.document to the provided document.
I would like to alter this code to so that the data is inserted in another thread, and the user can still click a button to view a section, without the data import hanging the UI.
Any help would be appreciated I have worked on this issue for a couple of days and not been able to solve it, even with the other similar questions on here. If there's any other information you require, please let me know!
Thank you
EDIT:
So far this question has received one down vote. If there is a way I could improve this question, or someone knows of a question I've not been able to find, could you please comment as to how or where? If there is another reason you are downvoting, please let me know, as I'm not able to understand the negativity, and would love to learn how to contribute better.
There are a couple of ways to this.
Since you are using UIManagedDocument you could take advantage of NSPrivateQueueConcurrencyType for initialize a new NSManagedObjectContext and use performBlock to do your stuff. For example:
// create a context with a private queue so access happens on a separate thread.
NSManagedObjectContext *context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
// insert this context into the current context hierarchy
context.parentContext = parentContext;
// execute the block on the queue of the context
context.performBlock:^{
// do your stuff (e.g. a long import operation)
// save the context here
// with parent/child contexts saving a context push the changes out of the current context
NSError* error = nil;
[context save:&error];
}];
When you save from the context, data of the private context are pushed to the current context. The saving is only visible in memory, so you need to access the main context (the one linked to the UIDocument) and do a save there (take a look at does-a-core-data-parent-managedobjectcontext-need-to-share-a-concurrency-type-wi).
The other way (my favourite one) is to create a NSOperation subclass and do stuff there. For example, declare a NSOperation subclass like the following:
//.h
#interface MyOperation : NSOperation
- (id)initWithDocument:(UIManagedDocument*)document;
#end
//.m
#interface MyOperation()
#property (nonatomic, weak) UIManagedDocument *document;
#end
- (id)initWithDocument:(UIManagedDocument*)doc;
{
if (!(self = [super init])) return nil;
[self setDocument:doc];
return self;
}
- (void)main
{
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] init];
[moc setParentContext:[[self document] managedObjectContext]];
// do the long stuff here...
NSError *error = nil;
[moc save:&error];
NSManagedObjectContext *mainMOC = [[self document] managedObjectContext];
[mainMOC performBlock:^{
NSError *error = nil;
[mainMOC save:&error];
}];
// maybe you want to notify the main thread you have finished to import data, if you post a notification remember to deal with it in the main thread...
}
Now in the main thread you can provide that operation to a queue like the following:
MyOperation *op = [[MyOperation alloc] initWithDocument:[self document]];
[[self someQueue] addOperation:op];
P.S. You cannot start an async operation in the main method of a NSOperation. When the main finishes, delegates linked with that operations will not be called. To say the the truth you can but this involves to deal with run loop or concurrent behaviour.
Hope that helps.
Initially I was just going to leave a comment, but I guess I don't have the privileges for it. I just wanted to point out the UIDocument, beyond the change count offers
- (void)autosaveWithCompletionHandler:(void (^)(BOOL success))completionHandler
Which shouldn't have the delay I've experienced with updating the change count as it waits for a "convenient moment".