Download JSON async crash - ios

Question

I download my Firebase database in json with AFNetworking 3. Everything works fine but there is a crash in the function cellForRoAtIndexPath.
Thanks
Work :
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
[manager GET:#"https://jojol-concours-lists.firebaseio.com/.json" parameters:URLParameters progress:nil success:^(NSURLSessionTask *task, id responseObject) {
self.contestArray = responseObject;
[_collectionView reloadData];
} failure:^(NSURLSessionTask *operation, NSError *error) {
NSLog(#"Error: %#", error);
}];
Work :
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return [self.contestArray count];
}
Not work : (NSDictionary *array = [self.contestArray objectAtIndex:indexPath.row];)
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
cellForItemAtIndexPath:(NSIndexPath *)indexPath {
DemoCollectionViewCell *retVal = [collectionView dequeueReusableCellWithReuseIdentifier:#"collectionViewCell"
forIndexPath:indexPath];
//////// Not work ///////
NSDictionary *array = [self.contestArray objectAtIndex:indexPath.row];
//////// Not work ///////
retVal.name.text = #"";
retVal.contentView.layer.cornerRadius = 10;
retVal.contentView.layer.masksToBounds = YES;
return retVal;
}
JSON :
{
"Concours-1" : {
"Description" : "Description du concours",
"Title" : "Titre"
},
"Concours-2" : {
"Description" : "Description du concours",
"Titre" : "iPhone 6"
}
}
Log Crash :
-[NSDictionaryI objectAtIndex:]: unrecognized selector sent to instance 0x61000086c8c0
2017-07-18 10:00:26.787 jojol67[7003:4420828] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryI objectAtIndex:]: unrecognized selector sent to instance 0x61000086c8c0'
*** First throw call stack:
(
0 CoreFoundation 0x000000010c084b0b __exceptionPreprocess + 171
1 libobjc.A.dylib 0x000000010e5c9141 objc_exception_throw + 48
2 CoreFoundation 0x000000010c0f4134 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132
3 CoreFoundation 0x000000010c00b840 ___forwarding_ + 1024
4 CoreFoundation 0x000000010c00b3b8 _CF_forwarding_prep_0 + 120
5 jojol67 0x000000010756db3f -[DEMOConcoursTableViewController collectionView:cellForItemAtIndexPath:] + 191
6 UIKit 0x000000010d162925 -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:isFocused:notify:] + 446
7 UIKit 0x000000010d162761 -[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:] + 35
8 UIKit 0x000000010d1679bd -[UICollectionView _updateVisibleCellsNow:] + 4764
9 UIKit 0x000000010d16d38e -[UICollectionView layoutSubviews] + 313
10 UIKit 0x000000010c8f355b -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1268
11 QuartzCore 0x000000010c6a4904 -[CALayer layoutSublayers] + 146
12 QuartzCore 0x000000010c698526 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 370
13 QuartzCore 0x000000010c6983a0 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
14 QuartzCore 0x000000010c627e92 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 294
15 QuartzCore 0x000000010c654130 _ZN2CA11Transaction6commitEv + 468
16 QuartzCore 0x000000010c654b37 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 115
17 CoreFoundation 0x000000010c02a717 CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 23
18 CoreFoundation 0x000000010c02a687 __CFRunLoopDoObservers + 391
19 CoreFoundation 0x000000010c00f720 __CFRunLoopRun + 1200
20 CoreFoundation 0x000000010c00f016 CFRunLoopRunSpecific + 406
21 GraphicsServices 0x00000001103c2a24 GSEventRunModal + 62
22 UIKit 0x000000010c830134 UIApplicationMain + 159
23 jojol67 0x000000010752ef5f main + 111
24 libdyld.dylib 0x000000010f31d65d start + 1
25 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
/////// Firebase realtime database ////////

Answer 1

Your id responseObject is not an array because your JSON contains an object not an array. App crashes because you are calling objectAtIndex on a NSDictionary object.
If you want to access this JSON as an array, you may want to format it to something like this,
[{
"Concours": 1,
"Description": "Description du concours",
"Title": "Titre"
}, {
"Concours": 2,
"Description": "Description du concours",
"Titre": "iPhone 6"
}]

Answer 2

It will help you for such responce:
NSDictionary *jsonDict =responseObject;
NSArray *allKeys = [jsonDict allKeys];
NSMutableArray *allDataArray = [NSMutableArray new];
for (int x = 0; x<allKeys.count; x++) {
NSString *key = [allKeys objectAtIndex:x];
[allDataArray addObject:[jsonDict valueForKey:key]];
// then reload your collection on allDataArray
}

Answer 3

Current JSON:
{
"Concours-1" : {
"Description" : "Description du concours",
"Title" : "Titre"
},
"Concours-2" : {
"Description" : "Description du concours",
"Titre" : "iPhone 6"
}
}
How it should be:
[
{
"Description": "Description du concours",
"Title": "Titre"
},
{
"Description": "Description du concours",
"Titre": "iPhone 6"
}
]

Answer 4

"-[NSDictionaryI objectAtIndex:]: unrecognized selector sent to instance 0x61000086c8c0 "
It seems that the self.contestArray is NSDictionary class;
You can log the responseObject it maybe a Dictionary , not Array;