UICollectionView different cell every x cells

Question

So I want to add ads inside my UIcollectionView. After every 4th folder, I want to show an ad (for a total of 3 times,hence the row 4,9 and 14).

I've tried the following:

  override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        if indexPath.row == 4 || indexPath.row == 9 || indexPath.row == 14 {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "AdUnitsCollectionViewCell", for: indexPath) as? AdUnitsCollectionViewCell
            //cell?.addSubview(AdUnitController().getBannerView(2))
            //cell?.view = AdUnitController().getBannerView(2)
            cell?.view.adUnitID = "/6499/example/banner"
            cell?.view.rootViewController = self
            cell?.view.load(DFPRequest())
            return cell!
        } else {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: FolderViewCellIdentifier, for: indexPath) as? FolderViewCell
        cell!.configure(folders![indexPath.row])
        return cell!
        }
    }

This does indeed show the ads 3 times after every 4th folder, but now my folder for that indexPath.row isn't shown anymore (4, 9 and 14). Is there a way I can add my ads inside the collectionview AND my folders as well?

Thanks!

Answer 1

First of all you must have to increase total number of item/row if you want to add it inside collection view (which will be total_folder + total_add) but as @bhmahler said : Just adding the number of rows is not enough, you then need to account for the negative offset

What you can do is you can keep a count of how many time it went inside the if block , if it went inside this block increase the count

if indexPath.row == 4 || indexPath.row == 9 || indexPath.row == 14 {
   count+=1 //which is initially set to zero 
}

Now in your else block you can simply minus the count from index path, like this

else {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: FolderViewCellIdentifier, for: indexPath) as? FolderViewCell
        cell!.configure(folders![indexPath.row-count])
        return cell!
    }

Make sure to set count=0 outside of collection view delegate methods

Sorry for the incomplete code as I don't know swift.Hope it helps

Answer 2

You will need to increase the number of rows if you want to show both an ad AND the folder

override func numberOfItems(inSection section: Int) -> Int {
   let count = //the count you were using before
   return count + floor(count/4) //add an ad every 4
}

override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    if indexPath.row % 4 == 0 && indexPath.row > 0 {  //assuming you don't want an ad as the first item
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "AdUnitsCollectionViewCell", for: indexPath) as? AdUnitsCollectionViewCell
        //cell?.addSubview(AdUnitController().getBannerView(2))
        //cell?.view = AdUnitController().getBannerView(2)
        cell?.view.adUnitID = "/6499/example/banner"
        cell?.view.rootViewController = self
        cell?.view.load(DFPRequest())
        return cell!
    } else {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: FolderViewCellIdentifier, for: indexPath) as? FolderViewCell
        cell!.configure(folders![indexPath.row])
        return cell!
    }
}

EDIT

A more holistic approach would be to modify your folders array(?) to support both AdUnitsCollectionViewCell and FolderViewCell data.
For example, if folders is an array of structs as

struct CellData {
    static enum CellDataType {
        case folder
        case ad
    }
    let type: CellDataType
    let data: //some type - you haven't shown whats required
}

There will need to be a method that injects an ad every 4 into the folders array and then you can switch on folders[indexPath.row].type to decide if you want to show an ad cell or a folder cell. You don't need to modify the numberOfItemsInSection method either.