Connecting Custom layout class to collection view in code

i have a small question about a custom layout class and i need to connect it to my collection view in code not by the story board because i create the whole project by code . any help, please ?

my main class

import UIKit
import Firebase
class UserProfileController: UICollectionViewController
override func viewDidLoad()
super.viewDidLoad()
collectionView?.backgroundColor = .white
//fetchUser()
collectionView?.dataSource = self
collectionView?.delegate = self
collectionView?.register(TestCell.self, forCellWithReuseIdentifier: mainCellId)



fileprivate let mainCellId = "mainCellId"
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: mainCellId, for: indexPath) as! TestCell

return cell


override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
return 15

override func numberOfSections(in collectionView: UICollectionView) -> Int
return 1




the custom layout class which need to connect it to the collection view in code not story board

import UIKit

struct UltraVisualLayoutConstants
struct Cell
static let standardHeight: CGFloat = 100
static let featuredHeight: CGFloat = 280
// static let standardWidth: CGFloat = 100
// static let featuredWidth: CGFloat = 280



class UltraVisualLayout: UICollectionViewLayout {
// amount which users need to scroll before featured cell changes
let dragOffset: CGFloat = 180.0
var cache = [UICollectionViewLayoutAttributes]()
//return item index of current featured cell
var featuredItemIndex: Int
get
//use max to ensure that featureditemindex never be < 0
return max(0 , Int(collectionView!.contentOffset.y / dragOffset))



// returns value between 0 and 1 to represent how close the next cell becomes the featured cell
var nextItemPercentegeOffset: CGFloat
get
return (collectionView!.contentOffset.y / dragOffset) - CGFloat(featuredItemIndex)


// return the width of collection view
var width: CGFloat
get

guard let width = collectionView?.bounds.width else return 0
return width


// return the height of collection view
var height: CGFloat
get
guard let height = collectionView?.bounds.height else return 0
return 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 content in collection view
override var 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(x: 0, y: 0, width: 0, height: 0)
var y: CGFloat = 0
for item in 0..<numberOfItems
let indexPath = NSIndexPath(item: item, section: 0)
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath as IndexPath)
attributes.zIndex = item
var height = standardHeight
if indexPath.item == featuredItemIndex
let yOffset = standardHeight * nextItemPercentegeOffset
y = collectionView!.contentOffset.y - yOffset
height = featuredHeight
else if indexPath.item == (featuredItemIndex + 1) && indexPath.item != numberOfItems
let maxY = y + standardHeight
height = standardHeight + max((featuredHeight - standardHeight) * nextItemPercentegeOffset, 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 cache whose frame intersects with the rect passed to the method
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]?
var layoutAttributes = [UICollectionViewLayoutAttributes]()
for attributes in cache
if attributes.frame.intersects(rect)
layoutAttributes.append(attributes)


return layoutAttributes


// return true so that layout is continuously invalidated as the user scrolls
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool
return true



1 Answer
1

You cannot set the layout programmatically if you don't have an initializer. From the docs:

layout

The layout object to use for organizing items. The collection
view stores a strong reference to the specified object. Must not be
nil.

Since you seem to be using the storyboard, you'll have to set it there.

Once you create you layout class in code, it will show up when you click you collection view on the storyboard. The default layout will be set to Flow, when you change it to Custom, a new class field will show up. When you click that, it will list your layout class. You can choose it and set it from there.

However if you are initializing your storyboard programmatically, then you just need to pass it as a parameter to your initializer.

var collectionView = UICollectionView(frame: yourFrame, collectionViewLayout: customCollectionViewLayout) // pass your custom collection view instance


collectionView

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