CollectionView cell does not change backgroundColor - ios

Question

As the title says, I'm incurred in a little trouble using UltraVisualLayout class. When I change the background color to my cell (using UltraVisualLayout as custom layout in the collectionView) cells do not appear to have color, instead if I change to standard flow layout, the cells change their background colors.
I use these lines to color the cells:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "squadraCell", for: indexPath)
switch (indexPath.row % 5)
{
// ho provato anche con cell.contentView.backgroundColor ma non funziona nemmeno così
case 0: cell.contentView.backgroundColor = UIColor.yellow()
case 1: cell.contentView.backgroundColor = UIColor.orange()
case 2: cell.contentView.backgroundColor = UIColor.red()
case 3: cell.contentView.backgroundColor = UIColor.green()
case 4: cell.contentView.backgroundColor = UIColor.blue()
default: break
}
return cell
}
Here my custom layout (https://www.raywenderlich.com/99087/swift-expanding-cells-ios-collection-views)
//
// UltravisualLayout.swift
// RWDevCon
//
// Created by Mic Pringle on 27/02/2015.
// Copyright (c) 2015 Ray Wenderlich. All rights reserved.
//
import UIKit
/* The heights are declared as constants outside of the class so they can be easily referenced elsewhere */
struct UltravisualLayoutConstants
{
struct Cell
{
/* The height of the non-featured cell */
static let standardHeight: CGFloat = 100
/* The height of the first visible cell */
static let featuredHeight: CGFloat = 280
}
}
class UltravisualLayout: UICollectionViewLayout
{
// MARK: Properties and Variables
/* The amount the user needs to scroll before the featured cell changes */
let dragOffset: CGFloat = 180.0
var cache = [UICollectionViewLayoutAttributes]()
/* Returns the item index of the currently featured cell */
var featuredItemIndex: Int
{
get
{
/* Use max to make sure the featureItemIndex is never < 0 */
return max(0, Int(collectionView!.contentOffset.y / dragOffset))
}
}
/* Returns a value between 0 and 1 that represents how close the next cell is to becoming the featured cell */
var nextItemPercentageOffset: CGFloat
{
get
{
return (collectionView!.contentOffset.y / dragOffset) - CGFloat(featuredItemIndex)
}
}
/* Returns the width of the collection view */
var width: CGFloat
{
get
{
return collectionView!.bounds.width
}
}
/* Returns the height of the collection view */
var height: CGFloat
{
get
{
return collectionView!.bounds.height
}
}
/* Returns the number of items in the collection view */
var numberOfItems: Int
{
get
{
return collectionView!.numberOfItems(inSection: 0)
}
}
// MARK: UICollectionViewLayout
/* Return the size of all the content in the collection view */
override func collectionViewContentSize() -> CGSize
{
let contentHeight = (CGFloat(numberOfItems) * dragOffset) + (height - dragOffset)
return CGSize(width: width, height: contentHeight)
}
override func prepare()
{
cache.removeAll(keepingCapacity: false)
let standardHeight = UltravisualLayoutConstants.Cell.standardHeight
let featuredHeight = UltravisualLayoutConstants.Cell.featuredHeight
var frame = CGRect.zero
var y: CGFloat = 0
for item in 0..<numberOfItems
{
let indexPath = NSIndexPath(item: item, section: 0)
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath as IndexPath)
/* Important because each cell has to slide over the top of the previous one */
attributes.zIndex = item
/* Initially set the height of the cell to the standard height */
var height = standardHeight
if indexPath.item == featuredItemIndex {
/* The featured cell */
let yOffset = standardHeight * nextItemPercentageOffset
y = collectionView!.contentOffset.y - yOffset
height = featuredHeight
} else if indexPath.item == (featuredItemIndex + 1) && indexPath.item != numberOfItems
{
/* The cell directly below the featured cell, which grows as the user scrolls */
let maxY = y + standardHeight
height = standardHeight + max((featuredHeight - standardHeight) * nextItemPercentageOffset, 0)
y = maxY - height
}
frame = CGRect(x: 0, y: y, width: width, height: height)
attributes.frame = frame
cache.append(attributes)
y = frame.maxY
}
}
/* Return all attributes in the cache whose frame intersects with the rect passed to the method */
func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]?
{
var layoutAttributes = [UICollectionViewLayoutAttributes]()
for attributes in cache
{
if attributes.frame.intersects(rect)
{
layoutAttributes.append(attributes)
}
}
return layoutAttributes
}
/* Return the content offset of the nearest cell which achieves the nice snapping effect, similar to a paged UIScrollView */
override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint
{
let itemIndex = round(proposedContentOffset.y / dragOffset)
let yOffset = itemIndex * dragOffset
return CGPoint(x: 0, y: yOffset)
}
/* Return true so that the layout is continuously invalidated as the user scrolls */
func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool
{
return true
}
}
Here my Xcode project https://www.dropbox.com/sh/7xcu118a9zb7673/AAD6t5zhIgKC5fUUpUTb-yA1a?dl=0
Could you help me?