ambiguous reference to member 'subscript' swift 3 - swift

Question

I am trying to create a UICollectionViewFlowLayout subclass and i am getting ambiguous reference to member 'subscript' error when i try to return the layoutAttributesForItem:
import UIKit
class FLCollectionViewFlowLayout: UICollectionViewFlowLayout {
var items = 0
let CELL_HEIGHT : CGFloat = 306.0
let CELL_WIDTH : CGFloat = 219.0
var cellInformation = Dictionary<NSIndexPath,UICollectionViewLayoutAttributes>()
var contentSize = CGSize.zero
override var collectionViewContentSize: CGSize {
return self.contentSize
}
override func prepare() {
super.prepare()
print("preparing layout")
items = 20
let sections = self.collectionView?.numberOfSections
var section = 0
var item = 0
var indexPath = NSIndexPath()
var contentWidth : CGFloat = 0.0
let contentHeight : CGFloat = CELL_HEIGHT + self.sectionInset.top + self.sectionInset.bottom
while section < sections! {
while item < (self.collectionView?.numberOfItems(inSection: section))! {
indexPath = NSIndexPath(item: item, section: section)
let xPos = CGFloat(item) * CELL_WIDTH
let yPos = CGFloat(section) * CELL_HEIGHT
let cellAttributes = UICollectionViewLayoutAttributes(forCellWith: indexPath as IndexPath)
cellAttributes.frame = CGRect(x: xPos, y: yPos, width: CELL_WIDTH, height: CELL_HEIGHT)
cellInformation[indexPath] = cellAttributes
item+=1
}
contentWidth = CGFloat((self.collectionView?.numberOfItems(inSection:section))!) * CELL_WIDTH
section+=1
}
self.contentSize = CGSize(width: contentWidth, height: contentHeight)
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var attributesInRect = [UICollectionViewLayoutAttributes]()
for cellAttributes in cellInformation.values {
if rect.intersects(cellAttributes.frame) {
attributesInRect.append(cellAttributes)
}
}
return attributesInRect
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return cellInformation[indexPath]! // <---- This is where i get the error
}
}
Any suggestion would be greatly appreciated .

Answer 1

In Swift 3 NSIndexPath has been replaced with native struct IndexPath
Change
...
var cellInformation = Dictionary<IndexPath,UICollectionViewLayoutAttributes>()
...
var indexPath = IndexPath()
...
indexPath = IndexPath(item: item, section: section)
...
let cellAttributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)