Possible to save an integer array using NSUserDefaults on iPhone?

Question

Is it possible to save an integer array using NSUserDefaults on the iPhone? I have an array declared in my .h file as: int playfield[9][11] that gets filled with integers from a file and determines the layout of a game playfield. I want to be able to have several save slots where users can save their games. If I do:

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
[prefs setObject: playfield forKey: @"slot1Save"];

I get a pointer error. If it's possible to save an integer array, what's the best way to do so and then retrieve it later?

Thanks in advance!

Answer 1

You can save and retrieve the array with a NSData wrapper

ie (w/o error handling)

Save

NSData *data = [NSData dataWithBytes:&playfield length:sizeof(playfield)];
[prefs setObject:data forKey:@"slot1Save"];

Load

NSData *data = [prefs objectForKey:@"slot1Save"];
memcpy(&playfield, data.bytes, data.length);

Answer 2

From Apple's NSUserDefaults documentation:

A default’s value must be a property list, that is, an instance of (or for collections a combination of instances of): NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary.

This is why you are getting the pointer error.

You have several options (in order of recommended usage):

1. Use an NSArray of NSArrays to store playField in your application
2. Keep playField as an array of int, but fill an NSArray with numbers before saving to NSUserDefaults.
3. Write your own subclass of NSArchiver to convert between an array of integers and NSData.