Corner Flow Layout In Swift

PSCornerFlowLayout.swift

import UIKit

class CornerFlowLayout: UICollectionViewFlowLayout {
    
    var itemTransform:CGFloat!
    
    
    
    override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        
        let oldItems = super.layoutAttributesForElementsInRect(rect)!
        let allItems = oldItems
        
        for (_, object) in allItems.enumerate() {
            let attributes:UICollectionViewLayoutAttributes = object
            self.updateCellAttributes(attributes)
        }
        return allItems
        
    }
    
    
    func updateCellAttributes(attributes: UICollectionViewLayoutAttributes) {
        
        
        let minY = CGRectGetMinY((self.collectionView?.bounds)!) + (self.collectionView?.contentInset.top)!
        let maxY = attributes.frame.origin.y
        let finalY = max(minY, maxY)
        
        
        
        var origin:CGPoint = attributes.frame.origin
        
        origin.y = finalY
        attributes.frame = CGRect(origin: origin, size: attributes.frame.size)
        attributes.zIndex = attributes.indexPath.row
        
        
    }
    
    
    override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
        return true
    }
    
    
}