Why does my application crash when loading an array from NSUserDefaults?

Question

I'm trying to load an array from the NSUserDefaults in an iPhone application. I set things up with this code:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
self.myarray_1 = nil;

but then my application crashes at the following line:

self.myarray_1 = [[NSMutableArray alloc] 
                   initWithArray: [defaults objectForKey:@"highscores"]];   

with the error

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', 
reason: '-[NSCFString count]: unrecognized selector sent to instance 0x796c710'

How can I solve this?

Answer 1

The error message says that an instance of NSString received a count message, but obviously it does not respond to it (ie does not implement such a message). Most likely the message was intended for an NSArray instance.

Did you accidentally save an NSString instead of an NSArray in your defaults for the key @"highscores" ? Maybe in one of your previous builds? To clear all user defaults, you could just delete the app from the simulator or your device and reinstall it.

Answer 2

Try this

self.myarray_1 = [[NSMutableArray alloc] initWithArray:(NSArray*)[defaults objectForKey:@"highscores"]]; 

and I am sure you have made variable myarray_1 as proparty of your this class.

Answer 3

The value in your app's defaults is a String, not an Array. You are probably setting the default to a string rather than an array elsewhere in your code. Look for where you're calling -[NSUserDefaults setObject:forKey:] with the highscores key as the second parameter. Either you are still passing in an NSString as the first argument, or you were at one point and it's still set in the app's preferences.