NSArray is not saving in NSUserDefaults [duplicate] - ios

Question

This question already has answers here:
How to store custom objects in NSUserDefaults
(7 answers)
Closed 9 years ago.
I am making a high score manager.
I load and save as follows:
-(void)load
{
NSMutableArray* scores = [NSMutableArray arrayWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:HIGH_SCORE_KEY]];
if(scores == nil)
{
highscores = [NSMutableArray array];
}
else
{
highscores = scores;
}
}
-(void)save
{
[[NSUserDefaults standardUserDefaults] setObject:highscores forKey:HIGH_SCORE_KEY];
}
I am storing HighScore objects:
#import <Foundation/Foundation.h>
#interface HighScore : NSObject
{
int score;
NSString* name;
}
-(int)score;
-(NSString*)name;
-(id)init;
-(id)initWithName:(NSString*)playerName andScore:(int)playerScore;
-(BOOL)isEqual:(id)object;
-(BOOL)isLessThan:(id)object;
#end
There is nothing particularly complex about this class. However, when I load, the load does not return nil but returns an empty array, indicating to me that serializing probably failed for some reason.
Any ideas?
Thanks

Answer 1

NSUserDefaults always returns immutable objects, even if the original object was mutable. It's in the documentation for objectForKey:
The returned object is immutable, even if the value you originally set was mutable.
You will need to create a copy of the returned object before you modify it, using [NSMutableArray arrayWithArray:]
Probably also best to use the arrayForKey method of NSUserDefaults if you're retrieving an array. Docs here: http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html
You can only store objects in NSUserDefaults. So you have to convert the array to an NSArray. However, NSArrays also only store objects, so you need to store the long values encapsulated in an NSNumber object:
//saving
NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];
NSMutableArray *arrayObj = [[NSMutableArray alloc] init];
long *arr;
arr = new long [10];
for(int i = 0 ; i<10 ; i++) {
[arrayObj addObject:[NSNumber numberWithLong:arr[i]]];
}
[standardDefaults setObject:arrayObj forKey:#"longArray"];
[arrayObj release];
//reading
NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];
NSArray *arrayObj = [standardDefaults objectForKey:#"longArray"];
long *arr;
arr = new long [10];
for(int i = 0 ; i<10 ; i++) {
arr[i] = [(NSNumber*)[arrayObj objectAtIndex:i] longValue];
}