使用 DataSource 和 Flowlayout 管理多個集合檢視

在這裡，我們管理多個集合，其中使用 didselect 事件委託方法。

extension ProductsVC: UICollectionViewDelegate, UICollectionViewDataSource{
        
        // MARK: - UICollectionViewDataSource
        func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
            guard collectionView == collectionCategory else {
                return arrOfProducts.count
            }
            return arrOfCategory.count
        }
        
        func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
            
            guard collectionView == collectionProduct else {
                  let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ProductCategoryCell", for: indexPath) as! ProductCategoryCell
                  cell.viewBackground.layer.borderWidth = 0.5
                  //Do some thing as per use
                  return cell
            }
            
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! ProductCell
            cell.contentView.layer.borderWidth = 0.5
            cell.contentView.layer.borderColor = UIColor.black.cgColor
            let json = arrOfProducts[indexPath.row]
            //Do something as per use
    
            return cell
        }
        
        func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
            guard collectionView == collectionCategory else {
                let json = arrOfProducts[indexPath.row]
                // Do something for  collectionProduct here
                return
            }
            let json = arrOfCategory[indexPath.row] as [String: AnyObject]
            let id = json["cId"] as? String ?? ""
            // Do something
        }
    }
    
    extension ProductsVC: UICollectionViewDelegateFlowLayout{
        
        // MARK: - UICollectionViewDelegateFlowLayout
        func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
            
            let collectionWidth = collectionView.bounds.width
            guard collectionView == collectionProduct else {
                var itemWidth = collectionWidth / 4 - 1;
                
                if(UI_USER_INTERFACE_IDIOM() == .pad) {
                    itemWidth = collectionWidth / 4 - 1;
                }
                return CGSize(width: itemWidth, height: 50)
            }
            
            var itemWidth = collectionWidth / 2 - 1;
            if(UI_USER_INTERFACE_IDIOM() == .pad) {
                itemWidth = collectionWidth / 4 - 1;
            }
            return CGSize(width: itemWidth, height: 250);
        }
        
        func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
            return 1
        }
        
        func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
            return 1
        }
        
    }