Updating view with slow and unreliable data

gistfile1.m

-(void)updateTextLabel {
    [self fetchTextAndThen:^(NSString *result){
        self.textLabel.text = result;
    }];
}

-(void)fetchTextAndThen:(void (^)(NSString *result))block {
    NSString *current = [[NSUserDefaults standardUserDefaults] objectForKey:@"Text"];
    dispatch_async(webQueue, ^{
        NSString *response = [self requestToURL:@"http://192.168.0.108:8888/getText" withData:@"" withMethod:@"GET"];
        
        dispatch_async(mainQueue, ^{
            if (![response isEqualToString:current] && response != nil) {
                [[NSUserDefaults standardUserDefaults] setObject:response forKey:@"Text"];
                [[NSUserDefaults standardUserDefaults] synchronize];
                block(response);
            }
        });
    });
    block(current);
}