“UICollectionViewCell”类型的值没有成员“page”

类型强制铸造如何 cell 到 PageCellCollectionViewCell 使用 as!

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: 
"cellID", for: indexPath) as! PageCellCollectionViewCell
    let page = pages[indexPath.item]
    cell.page = page
    return cell
}