NSdata length crash on device - iphone

Question

While running this code:
NSData *archivedSavedData = [[NSData alloc] init];
archivedSavedData = [defaults objectForKey:#"listOfAccessNumbers"];
NSLog(#"archivedSavedData length is %d", [archivedSavedData length] );
I am getting this crash error (last line) only when running on a device that is connected:
[__NSCFArray length]: unrecognized selector sent to instance 0x2398a0
2012-03-13 20:25:33.088[7301:707] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFArray length]: unrecognized selector sent to instance 0x2398a0'
* First throw call stack:
(0x34dbc88f 0x361e3259 0x34dbfa9b 0x34dbe915 0x34d19650 0xccb1b 0x31e13e33 0x31e38629 0x31dfcd7d 0x31ebf4dd 0x31e0555d 0x31e05579 0x31e0540b 0x31e053e7 0xcfedf 0x31e12e53 0x31e0c985 0x31ddac6b 0x31dda70f 0x31dda0e3 0x3600f22b 0x34d90523 0x34d904c5 0x34d8f313 0x34d124a5 0x34d1236d 0x31e0ba13 0x31e08e7d 0xcfd39 0xcbe28)
terminate called throwing an exception
This doesn't happen when running on the simulator or directly on the device with a distribution profile (through testflight for example).
Does anyone know how such a behavior could happen only in this case?
Thanks.
UPDATE: when trying to replace length with count I get this complication error: "No visible #interface for 'NSData' declares the selector 'count'"
UPDATE2: I understand that it should be an NSArray rather than an NSData, but my problem is that I did store archived NSData cause my array consists of custom objects, so I had to archived this data into NSData format when saving in NSUserDefault. How else should I approach that otherwise?
Thats how I store the data:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array];
[defaults setObject:data forKey:#"listOfAccessNumbers"];
array is an array of custom objects of the form of:
#interface NumberDataObj : NSObject {
NSString *inputName;
NSString *inputNum;
}

Answer 1

The error message says:
-[__NSCFArray length]: unrecognized selector sent to instance
That means that archivedSavedData is an array and that it doesn't (obviously) respond to length so you should declare archivedSavedData as an array and use count instead.
NSArray *archivedSavedData = [defaults objectForKey:#"listOfAccessNumbers"];
NSLog(#"archivedSavedData length is %d", [archivedSavedData count]);
Now, as to why this doesn't happen when running on the simulator, my guess is that your test scenarios don't make this part of the code get called.
EDIT
If you want to retrieve the data as NSData then use the method dataForKey:
NSData *archivedSavedData = [defaults dataForKey:#"listOfAccessNumbers"];
NSLog(#"archivedSavedData length is %d", [archivedSavedData length]);
The documentation says for dataForKey:
Return Value
The data object associated with the specified key, or nil if the key does not exist or its value is not an NSData object.
and for arrayForkey:
Return Value
The array associated with the specified key, or nil if the key does not exist or its value is not an NSArray object.
So aways use the appropriate method when you know the type of the data to avoid problems like this.

Answer 2

You have two problems as the code is written:
1) You allocate a variable called archivedSavedData that you reassign on the following line without releasing. This is okay if you are working with ARC, but the first line would then be unnecessary.
2) The second problem is that the object corresponding to the key #"listOfAccessNumbers" stored in your defaults object is of type NSArray. NSArray responds to the selector count, not length. Maybe you should look more closely at this object and recode accordingly.
Hope this helps :)

Answer 3

It's because [defaults objectForKey:#"listOfAccessNumbers"] returns an NSArray, not an NSData object.