CODEWITHSUNDEEP
iosobjective-cuilabelnsnotificationcenter
Max_Power89
Max_Power89

Reputation: 1770

setText in UIlabel after notification call has no effect

i want update the text of my label every time i receive notification from nsmanageObjContext.

this is my code for add the observer:

- (IBAction)requestFotPhoto {

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(updateLabel) name:NSManagedObjectContextDidSaveNotification
                                           object:self.facebook.managedObjectContext];

and this is the method for update the label:

-(void)updateLabel
{
        NSString *text = [NSString stringWithFormat:@"Downalad %i pictures",[Photo NumeberOfAllPhotosFromContext:self.facebook.managedObjectContext]];
        dispatch_async(dispatch_get_main_queue(), ^{
            //UIKIT method
            NSLog(@"text %@",text);
            [self.downlaodLabel setText:text];
        });
}

i assume that updateLabel is execute in a another thread, so i execute the instructions for update the label on the main thread, but this code has no effect. where is the problem?

obviously the NSlog print the right message!

thanks!

Upvotes: 1

Views: 473

Answers (2)

crifan
crifan

Reputation: 14328

seems like:

  • your should move your NSNotificationCenter addObserver code, from your (IBAction)requestFotPhoto (seems is some button click event handler, which only run after user tapped) to viewDidLoad

shold like this:

- (void)viewDidLoad {
    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateLabel) name:NSManagedObjectContextDidSaveNotification object:self.facebook.managedObjectContext];
}
  • and for noficacation handler, not use dispatch_async

should like this:

- (void)updateLabel:(NSNotification *) notification {
    NSLog (@"updateLabel:  notification=%@", notification);
    if ([[notification name] isEqualToString: NSManagedObjectContextDidSaveNotification]) {
        NSDictionary *passedInUserInfo = notification.userInfo;
        NSString *yourText = [passedInUserInfo objectForKey:@"dataKey"];

        //UIKIT method
        NSLog(@"yourText=%@",yourText);
        [self.downlaodLabel setText:yourText];
    }
}
  • and somewhere else should send the text:
NSString *newText = @"someNewText";
NSDictionary *passedInfo = @{@"dataKey": newText};
[[NSNotificationCenter defaultCenter] postNotificationName:NSManagedObjectContextDidSaveNotification object: self userInfo:passedInfo];

for more detail pls refer another post answer

Upvotes: 0

Stanislav
Stanislav

Reputation: 410

In your situation you don't need to use dispatch_async, because notification handlers are run in the main thread. They are executed in a main loop on idle moments — sorry if I'm wrong with techincal words, english is not native for me.

And one more thing: you should't reference self from blocks, because self points to your block, and block points to self — they're not going to be released. If you really want to do it, you can read this question.

Upvotes: 0

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