iOS Terminating app due to uncaught exception 'NSUnknownKeyException'

Question

I am pretty new to objective c and iOS programming, and I have this pretty strange error. The app in question initializes a NSMutableArray with a preset set of values of a custom type I made using NSObject. Which is manipulated by the app. If new values are added during app run time, they are saved using NSUserDefaults, and are brought up from NSUserDefaults along with the default values on next app open.

This is the error I get:

Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<__NSCFConstantString 0xb404> valueForUndefinedKey:]: this class is not key value coding-compliant for the key score.'
*** First throw call stack:
(0x1c9b012 0x10d8e7e 0x1d23fb1 0xb84d1d 0xaf100b 0xaf0fbd 0xb0f247 0xb3023c 0xb30056 0x3e40 0x3c5f 0x11f5ad 0x10ec705 0x202c0 0x20258 0x242ff4 0x10ec705 0x202c0 0x20258 0xe1021 0xe157f 0xe1056 0x246af9 0x10ec705 0x202c0 0x20258 0xe1021 0xe157f 0xe06e8 0x4fcef 0x4ff02 0x2dd4a 0x1f698 0x1bf6df9 0x1bf6ad0 0x1c10bf5 0x1c10962 0x1c41bb6 0x1c40f44 0x1c40e1b 0x1bf57e3 0x1bf5668 0x1cffc 0x290d 0x2835)
libc++abi.dylib: terminate called throwing an exception

I am not quite sure what the error is or how to go about debugging it.

Previously this code worked flawlessly, all I did was remove one or two elements from the preset default list of elements, and in the simulator, simulated deleting the app, and recompiled the code. Ever since my program crashes, with the above message, and I can't figure out how to fix it.

So if someone can give me some help on how to go about debugging this, that would be wonderful. I can attach code as needed, i'm not sure what code would be relevant to be shown, and it may be too much to post all the code involved in the project.

Code to encode and decode the properties of my custom Name NSObject class called name.h:

-(void)encodeWithCoder:(NSCoder *)encoder
{
    [encoder encodeObject:self.name forKey:@"name"];
    [encoder encodeInteger:self.score forKey:@"score"];

}

-(id)initWithCoder:(NSCoder *)decoder
{
    if((self = [super init]))
    {
        self.name = [decoder decodeObjectForKey:@"name"];
        self.score = [decoder decodeIntegerForKey:@"score"];
    }

    return self;
}

Retrieving Data from class, incase this matters, this code occurs in appdelegate.m:

NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:@"dataArray"];


NSInteger score = 0;


NSMutableArray *temp = [[NSMutableArray alloc] initWithObjects:@"name", nil];

NSMutableArray *tempList = [[NSMutableArray alloc] init];

for(NSString *y in temp)
{
    Name *name = [[Name alloc] init];
    name.name  = y;
    name.score = score;
    [tempList addObject:name];


}

if (data)
{

    NSArray *list = [NSKeyedUnarchiver unarchiveObjectWithData:data];
   NSMutableArray *names = [[NSMutableArray alloc]initWithArray:list];
  // [_nameList addObjectsFromArray:temp];
    NSMutableArray *t = [[names arrayByAddingObjectsFromArray:tempList ] mutableCopy];

    _nameList = [[NSMutableArray alloc]init];

    [_nameList addObjectsFromArray:t];


}
else 
{
    //First time load or data is not saved yet
    _nameList = [[NSMutableArray alloc] initWithObjects:@"name", nil];

}

saving the array at close time:

- (void)applicationWillTerminate:(UIApplication *)application
{
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
NSData *data =[NSKeyedArchiver archivedDataWithRootObject:_nameList];


[[NSUserDefaults standardUserDefaults] setObject:data forKey:@"dataArray"];
}

same code is in applicationDidEnterBackground.

code to sort by 'score'

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:    (UIViewController *)viewController
{


    if(viewController == _viewController3)
    {
        [self sortNames:_nameList];
        [[(ThirdViewController*)_viewController3 topList] reloadData];

    }
}

-(void)sortNames:(NSMutableArray*)test
{



NSArray* temp = [[NSArray alloc] initWithArray:test];


NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"score" ascending:NO];
NSArray *sortedLinks = [[temp sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]] mutableCopy];

_nameList = (NSMutableArray*) sortedLinks;
}

Answer 1

Here's my two cents. You have this line:

[encoder encodeObject:self.name forKey:@"name"];

And then this line:

Name *name = [[Name alloc] init];

This makes me think that the "self.name" property is one of these "Name" custom subclasses.

I believe that if you make a custom subclass and you want it to encodewithcoder, you have to add the encodewithcoder method to your custom subclass and have it encodewithcoder all of its properties and instance variables as primitively as you can.

Meaning, your Name class needs to have its own encodewithcoder method that encodes all of its properties and instance variables that have been stored as factory objects or c primitives.

Edit: I'm still pretty new and value my rep. If I'm wrong, please comment and I'll delete but please don't downvote me to oblivion

Answer 2

Here:

_nameList = [[NSMutableArray alloc] initWithObjects:@"name", nil];

you are adding an NSString to the _nameList array. Later you save that array. The next time you load that array, you have the NSString @"name" in it. I guess at some point you iterate through the items in _nameList and try to get or set the score, since you are calling this on a subclass of NSString you get the NSUnknownKeyException.

I think what you want to is to replace the line above with something like this: (assuming the class in your name.h file you mentioned above is called Name)

Name *newName = [[Name alloc] init]; //or initialize the way you need to
_nameList = [[NSMutableArray alloc] initWithObjects:newName, nil];