xcode Converting UITableView to UICollectionView (no valid cell) - xcode

Question

EDIT: I should specify that this only happens when I attempt to use the UICollectionViewFlowLayout, not when I try to use a custom view. But either way nothing ever shows up on the CollectionView though it was working just fine before I converted from a TableView.)
So I've been trying to convert a UITableView that I had into a UICollectionView. So far so good. But when I try to run the app it gives me the error:
'the collection view's data source did not return a valid cell from -collectionView:cellForItemAtIndexPath: for index path {length = 2, path = 0 - 0}'
I checked all the similar questions and answers here... so in my viewDidLoad I have (tableView is actually a UICollectionView):
UINib * placeCell = [UINib nibWithNibName:#"Shops" bundle:nil];
[self.tableView registerNib:placeCell
forCellWithReuseIdentifier:CellIdentifier];
#pragma mark - UICollectionViewDataSource
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UICollectionView *)tableView numberOfItemsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return [_entries count];
//return 5;
}
- (void)tableView:(UICollectionView *)tableView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
if (indexPath.item == [_entries count]-1 && page > 1) {
NSLog(#"load more");
//add footer view loading
if (c_page == page) {
// _tableView.tableFooterView = nil;
}
else
{
c_page++;
[self loadPlace:c_page];
}
}
}
- (UICollectionViewCell *)tableView:(UICollectionView *)tableView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
PlaceCell *cell = (PlaceCell *)[tableView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
UINib * placeCell = [UINib nibWithNibName:#"Shops" bundle:nil];
//cell = [cellLoader instantiateWithOwner:self options:nil];
NSArray *topLevelItems = [placeCell instantiateWithOwner:self options:nil];
cell = [topLevelItems objectAtIndex:0];
Place *p = [_entries objectAtIndex:indexPath.row];
cell.placeName.text = p.PName;
NSLog (#"p:%#", p.PName")
cell.placeImg.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:p.PImage]]];
return cell;
}
I went into the xib of the UICollectionViewCell (PlaceCell) and made sure that "Cell" was the reuseidentifier. And I made sure that the datasource and delegate were connected to file's owner in the collectionView.
I also noticed that when I use a custom layout instead of the flow layout (like this one: https://github.com/ShadoFlameX/PhotoCollectionView/blob/master/CollectionViewTutorial/BHPhotoAlbumLayout.m ) it doesn't give me that error... but my collectionview still isn't populated.
So I'm wondering if there's some sort of log I can run or something I can do to figure out what's going wrong. Because I've tried all the solutions I've seen and it hasn't gotten me anywhere.

Answer 1

When you make a cell in a xib file you should register the xib, not the class. Also, when you register either the class or xib (or make the cell in the storyboard), you don't need an if (cell==nil) clause because your cell will never be nil when you dequeue it with dequeueReusableCellWithReuseIdentifier:forIndexPath:. You should delete that clause.

Answer 2

So the problem is: "Switched from UITableView to UICollectionView and no valid cell is being returned." It is really a two part answer. The crux of which is every instance of UITableView...
_tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 50, self.view.bounds.size.width, self.view.bounds.size.height-50)];
...you want to turn into "CollectionView"
_collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 50, self.view.bounds.size.width, self.view.bounds.size.height-50)];
Everything that's a "row":
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
...you'll want to turn into an "item."
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
Ultimately I had to delete the following section entirely:
UINib * placeCell = [UINib nibWithNibName:#"Shops" bundle:nil];
//cell = [cellLoader instantiateWithOwner:self options:nil];
NSArray *topLevelItems = [placeCell instantiateWithOwner:self options:nil];
cell = [topLevelItems objectAtIndex:0];
My best guess is that the Nib was being loaded twice and that Xcode was complaining that the data wasn't being loaded by the original. So getting rid of that second entry got my cells loaded and populated with data. Hope this helps someone.