Use more than one UICollectionViews in a ViewController - ios

Question

I tried to use two UICollectionViews in a single ViewController. Application crashed with the following error
reason: 'could not dequeue a view of kind: UICollectionElementKindCell with identifier ItemCell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard
This is my implementation how looks like
HomeViewController.h
UICollectionView *colloctionViewItems;
UICollectionView *colloctionViewCats;
#property (nonatomic, retain) IBOutlet UICollectionView *colloctionViewItems;
#property (nonatomic, retain) IBOutlet UICollectionView *colloctionViewCats;
HomeViewController.m
#synthesize colloctionViewCats, colloctionViewItems;
- (void)viewDidLoad{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
// read ItemList plist
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
NSDictionary *dicCats = [appDelegate readPlistIntoDictWithFile:#"CatagoryList.plist"];
// arrCategories
arrCats = [[NSArray alloc]initWithArray:[dicCats objectForKey:#"Catagories"]];
[self.colloctionViewItems registerClass:[ItemCell class] forCellWithReuseIdentifier:#"ItemCell"];
[self.colloctionViewCats registerClass:[CatCell class] forCellWithReuseIdentifier:#"CatCell"];
[colloctionViewItems reloadData];
[colloctionViewCats reloadData];
}
#pragma mark for Collection View Delegate methods
- (NSInteger)numberOfSectionsInCollectionView: (UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section
{
if(view == colloctionViewItems){
return [arrCats count];
}
if(view == colloctionViewCats){
return [arrCats count];
}
return 0;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
return CGSizeZero;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
ItemCell *iCell = [cv dequeueReusableCellWithReuseIdentifier:#"ItemCell" forIndexPath:indexPath];
CatCell *cCell = [cv dequeueReusableCellWithReuseIdentifier:#"CatCell" forIndexPath:indexPath];
if(cv == colloctionViewItems){
iCell.lblBtnTitle.text = [arrCats objectAtIndex:indexPath.row];
return iCell;
}
if(cv == colloctionViewCats){
cCell.lblBtnTitle.text = [arrCats objectAtIndex:indexPath.row];
return cCell;
}
return iCell;
}
If I removed one UICollectionView, all works fine. Any ideas please.
FYI: I have created Custom Collection Cell class as "ItemCell" and "CatCell" correctly (without using nibs)

Answer 1

It's because you dequeue both cell at the same time, even if the collection view hasn't contain the right cell. You should first check which collection view is asking about cell and after that dequeue the right one:
- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
if(cv == colloctionViewItems){
// Item collection view contain item cell so you can safety dequeue it.
// if you try to dequeue CatCell it will fail this is why you had this issue before
ItemCell *iCell = [cv dequeueReusableCellWithReuseIdentifier:#"ItemCell" forIndexPath:indexPath];
iCell.lblBtnTitle.text = [arrCats objectAtIndex:indexPath.row];
return iCell;
}
if(cv == colloctionViewCats){
CatCell *cCell = [cv dequeueReusableCellWithReuseIdentifier:#"CatCell" forIndexPath:indexPath];
cCell.lblBtnTitle.text = [arrCats objectAtIndex:indexPath.row];
return cCell;
}
return nil;
}