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POUpdating an NSArray when NSUserDefaults is updated`
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copied!<p>I have an application that pulls a list of the top places on flickr and returns the recent photos posted to those places. That is all done dynamically. I am also storing a list of recent images the user has viewed to NSUserDefaults. The data that flickr needs in order to pull up an image is stored in an NSDictionary, so I am writing the NSDictionary to an array, and then storing said array in NSUserDefaults. This is for a learning project, so I'm required to use NSUserDefaults, even if there is likely a better way. </p> <p>At this point, ALMOST everything works great. However, I am flummoxed on a method of updating the Recent Images after a user views a new image in the dynamic views. NSUserDefaults updates without issue, and the additional recent images show if I shut down the app and restart it. </p> <p>Here is my code where I write to defaults. Doesn't seem to be an issue here. </p> <pre><code>idvc = [[ImageDisplayViewController alloc] init]; idvc.flickrInfo = [placePhotosArray objectAtIndex:[indexPath row]]; // Add data to NSUserDefaults NSUserDefaults *currentDefaults = [NSUserDefaults standardUserDefaults]; NSData *dataFromRecentArray = [currentDefaults objectForKey:@"recentImages"]; if (dataFromRecentArray != nil) { NSArray *oldArray = [NSKeyedUnarchiver unarchiveObjectWithData:dataFromRecentArray]; if (oldArray != nil) { currentRecentImagesArray = [oldArray mutableCopy]; } else { currentRecentImagesArray = [[NSMutableArray alloc] init]; } } else { currentRecentImagesArray = [[NSMutableArray alloc] init]; } [currentRecentImagesArray addObject:idvc.flickrInfo]; [[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:currentRecentImagesArray] forKey:@"recentImages"]; [currentRecentImagesArray release]; [self.navigationController pushViewController:idvc animated:YES]; [idvc release]; </code></pre> <p>Here is where I am reading the data back out</p> <pre><code>- (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; NSUserDefaults *currentDefaults = [NSUserDefaults standardUserDefaults]; NSData *dataFromRecentImages = [currentDefaults objectForKey:@"recentImages"]; if (dataFromRecentImages != nil) { NSArray *currentArray = [NSKeyedUnarchiver unarchiveObjectWithData:dataFromRecentImages]; recentImagesArray = [[NSArray alloc] initWithArray:currentArray]; } } </code></pre> <p>Honestly, the requirements for the assignment are fulfilled, I could stop here if I wanted to. But I'd like to understand how this is done. I am pretty good at extrapolating generic code examples and applying it to mine, so you don't have to fix MY specific problem. Just need to know how to update a variable that's value is set from user defaults after defaults have been updated. </p>

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