Snippet untuk create collection view cell bisa tertata pada screen.

Snippet-GalleryCollectionView.swift

...

// Calculate cells spacing and size
var cellSize: CGFloat = 0
var isDecided = false
var cellSpacing:CGFloat = 1
let cellCounts:CGFloat = 3

while !isDecided {
    let value = (UIScreen.main.bounds.width-cellSpacing*(cellCounts+1))/cellCounts
    if value.truncatingRemainder(dividingBy: floor(value)) > 0 {
        cellSpacing += 1
        continue
    }
    cellSize = value
    isDecided = true
}

// Setup cells spacing and insets
let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.sectionInset = UIEdgeInsets(top: cellSpacing, left: cellSpacing, bottom: cellSpacing, right: cellSpacing)
layout.minimumInteritemSpacing = cellSpacing
layout.minimumLineSpacing = cellSpacing

collectionView.layout = layout

...