Slowly pages, not the snappy paging behavior but still nice.

PagingCollectionViewController.swift

import UIKit

private let reuseIdentifier = "Cell"

class CollectionViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

    /* Return item size */
    var itemSize: CGSize {
        let layout = self.collectionViewLayout as! UICollectionViewFlowLayout
        return layout.itemSize
    }
    
    /* Return spacing: Interitem */
    var interItemSpacing: CGFloat {
        let layout = self.collectionViewLayout as! UICollectionViewFlowLayout
        return layout.minimumInteritemSpacing
    }
    
    /* Get section inset */
    var sectionInset: UIEdgeInsets {
        let layout = self.collectionViewLayout as! UICollectionViewFlowLayout
        return layout.sectionInset
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    // MARK: UICollectionViewDataSource
    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 10
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath)
        
        return cell
    }
    
    /* Custom Paging */
    override func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        
        // Page size delta
        let pagingDelta = floor(scrollView.contentOffset.x / self.itemSize.width)
        
        // Spacing and Inset
        let spacing = self.interItemSpacing - (self.sectionInset.left + self.sectionInset.right)
        
        // Calculate offset depending on direction
        let offset = (pagingDelta + ((velocity.x > 0) ? 1 : -1)) * (self.itemSize.width - spacing)
        
        // Target point
        let target = CGPoint(x: offset, y: 0)
        targetContentOffset.pointee = target
    }
}