NSarray of NSdictionaries - iphone

Question

I am loading some values in UItableview from an array of dictionary values. I then alter the dictionary in the array by adding one more key value object as below
NSMutableDictionary *rowDict = [tableList objectAtIndex:arrayindex];
[rowDict setObject:#"download successfull" forKey:#"downloadstatus"];
but after this when I try retrieveing value from dictionary in the array as below
NSMutableDictionary *rowDict = [tableList objectAtIndex:arrayindex];
NSString *SelectedState = (NSString*)[rowDict objectForKey:#"downloadstatus"];
it crashes ... can any one help me out to fix this
this is the crash display on my consol
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSConcreteMutableData objectForKey:]: unrecognized selector sent to instance 0x61a8270'
*** Call stack at first throw:
(
0 CoreFoundation 0x003b0be9 __exceptionPreprocess + 185
1 libobjc.A.dylib 0x015c15c2 objc_exception_throw + 47
2 CoreFoundation 0x003b26fb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
3 CoreFoundation 0x00322366 ___forwarding___ + 966
4 CoreFoundation 0x00321f22 _CF_forwarding_prep_0 + 50
5 SifyMyStorage 0x0003b35b -[DownloadListViewController tableView:cellForRowAtIndexPath:] + 314
6 UIKit 0x00ec67fa -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 634
7 UIKit 0x00ebc77f -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 75
8 UIKit 0x00ed1450 -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 1561
9 UIKit 0x00ec9538 -[UITableView layoutSubviews] + 242
10 QuartzCore 0x009f4451 -[CALayer layoutSublayers] + 181
11 QuartzCore 0x009f417c CALayerLayoutIfNeeded + 220
12 QuartzCore 0x009ed37c _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 310
13 QuartzCore 0x009ed0d0 _ZN2CA11Transaction6commitEv + 292
14 QuartzCore 0x00a1d7d5 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 99
15 CoreFoundation 0x00391fbb __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 27
16 CoreFoundation 0x003270e7 __CFRunLoopDoObservers + 295
17 CoreFoundation 0x002efbd7 __CFRunLoopRun + 1575
18 CoreFoundation 0x002ef240 CFRunLoopRunSpecific + 208
19 CoreFoundation 0x002ef161 CFRunLoopRunInMode + 97
20 GraphicsServices 0x02ead268 GSEventRunModal + 217
21 GraphicsServices 0x02ead32d GSEventRun + 115
22 UIKit 0x00e6142e UIApplicationMain + 1160
23 SifyMyStorage 0x000020b8 main + 102
24 SifyMyStorage 0x00002049 start + 53
)
terminate called after throwing an instance of 'NSException'

Answer 1

See if you have allocated the object and also get the count of dictionary , if the value is being added also see if u have declared NSmutabledictionary or just NSdictionary ... a view at your class having the code would be more helpful to sort out your problem

Answer 2

Ok, a couple things:
-the code you posted is fine. That's not the issue. The (NSString *) cast is unnecessary, but not an issue.
-there is an issue with your NSArray tablelist. If you are really adding only NSMutableDictionary to the array, then either you are doing that wrong, or your array is going out of scope and when you think you are accessing your array, you are accessing something else in memory at that location.
-How are you retaining your reference to tablelist within the controller?
-Change your second code block to this and I'll bet you find your problem (retainCount on one of these object == 0):
NSLog(#"retain count=%d",[tableList retainCount]);
NSMutableDictionary *rowDict = [tableList objectAtIndex:arrayindex];
NSLog(#"retain count=%d",[rowDict retainCount]);
NSString *SelectedState = [rowDict objectForKey:#"downloadstatus"];

Answer 3

you r not alloc the NSMutableDictionary so the NSMutableDictionary is empty and your app crashes.
NSMutableDictionary *rowDict = [[NSMutableDictionary alloc]init];
rowDict = [tableList objectAtIndex:arrayindex];
NSString *SelectedState = [rowDict objectForKey:#"downloadstatus"];
best of luck