UICollectionView spacing margins

Question

I have a UICollectionView which shows photos. I have created the collectionview using UICollectionViewFlowLayout. It works good but I would like to

Answer 1

Modern Swift, Automatic Layout Calculation

While this thread already contains a bunch of useful answers, I want to add a modern Swift version, based on William Hu's answer. It also improves two things:

• The spacing between different lines will now always match the spacing between items in the same line.
• By setting a minimum width, the code automatically calculates the number of items in a row and applies that style to the flow layout.

Here's the code:

// Create flow layout
let flow = UICollectionViewFlowLayout()

// Define layout constants
let itemSpacing: CGFloat = 1
let minimumCellWidth: CGFloat = 120
let collectionViewWidth = collectionView!.bounds.size.width

// Calculate other required constants
let itemsInOneLine = CGFloat(Int((collectionViewWidth - CGFloat(Int(collectionViewWidth / minimumCellWidth) - 1) * itemSpacing) / minimumCellWidth))
let width = collectionViewWidth - itemSpacing * (itemsInOneLine - 1)
let cellWidth = floor(width / itemsInOneLine)
let realItemSpacing = itemSpacing + (width / itemsInOneLine - cellWidth) * itemsInOneLine / max(1, itemsInOneLine - 1))

// Apply values
flow.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
flow.itemSize = CGSize(width: cellWidth, height: cellWidth)
flow.minimumInteritemSpacing = realItemSpacing
flow.minimumLineSpacing = realItemSpacing

// Apply flow layout
collectionView?.setCollectionViewLayout(flow, animated: false)