This is a sample of a Centered CollectionView Flow Layout

CollectionViewCenterLayout.swift

class CollectionViewRow {
    ...
  
    var rowWidth: CGFloat {
        return attributes.reduce(0, { result, attribute -> CGFloat in
            return result + attribute.frame.width
        }) + CGFloat(attributes.count - 1) * spacing
    }
    
    func centerLayout(collectionViewWidth: CGFloat) {
        let padding = (collectionViewWidth - rowWidth) / 2
        var offset = padding
        for attribute in attributes {
            attribute.frame.origin.x = offset
            offset += attribute.frame.width + spacing
        }
    }
}