NSMutableArray

[loddy1234]

I have some data stored in a NSMutableArray as NSNumbers. how can i save the mutable array? It is declared in the app delegate so I know I can use the

- (void)applicationWillTerminate:(UIApplication *)application {
  }

to save it, and I can use the

- (void)viewDidLoad {
}

to load it but what code do I use in the applicationWillTerminate method to save it?

[Duncan C]

Originally Posted by loddy1234

I have some data stored in a NSMutableArray as NSNumbers. how can i save the mutable array? It is declared in the app delegate so I know I can use the

- (void)applicationWillTerminate:(UIApplication *)application {
  }

to save it, and I can use the

- (void)viewDidLoad {
}

to load it but what code do I use in the applicationWillTerminate method to save it?

I would advise against saving in applicationWillTerminate. That method doesn't get called under OS 4.x

I would suggest saving your array every time it changes.

NSUserDefaults would work quite nicely.

#define K_ARRAY_KEY @"array_key"

Define numberArray as a retained property of the object that needs to use it, or your app delegate,
if you need access to it throughout your app.

- (void) saveData
{
  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
  [defaults setObject: self.numberArray forKey: K_ARRAY_KEY];
  [defaults synchronize];
}

//Add this code to your applicationDidFinishLaunching/application:didFinishLaunchingWithOptions:
//method (or viewDidLoad, if you just need the array in a view controller)

  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
  NSArray* tempArray = [defaults objectForKey: K_ARRAY_KEY];

  //the object comes back from user defaults as an NSArray, so copy it to a mutable array
  self.numberArray = [NSMutableArray arrayWithCapacity: [tempArray count]];
  [self.numberArray setArray: tempArray];

Note that saving a container object like an array to user defaults only works if every object in the array is a "plist" object (NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary).

[RLScott]

applicationWillTerminate can indeed be called from iOS 4 if you have not marked your info.plist to enable background running. But if you have enabled background running for iOS 4, then Duncan is right that it will not be called.

You could save the array every time it changes. But depending on how your array is used in your application, that could run into performance problems.

I have found it quite safe to save state in both applicationWillTerminate and applicationDidEnterBackground (using a third method that I call from both of these). As long as your app or the iPhone does not crash, you can count on on or the other of these methods to be called. And doing things those way will allow you to target iOS 3.x as well.

[Duncan C]

Originally Posted by RLScott

applicationWillTerminate can indeed be called from iOS 4 if you have not marked your info.plist to enable background running. But if you have enabled background running for iOS 4, then Duncan is right that it will not be called.

You could save the array every time it changes. But depending on how your array is used in your application, that could run into performance problems.

I have found it quite safe to save state in both applicationWillTerminate and applicationDidEnterBackground (using a third method that I call from both of these). As long as your app or the iPhone does not crash, you can count on on or the other of these methods to be called. And doing things those way will allow you to target iOS 3.x as well.

All true.

I generally save changes to user defaults as soon as I make them, except in a loop. In that case, I wait until a set of changes is complete, and then save updates. Obviously you need to test performance and adjust accordingly.