1import UIKit
2
3class HorizontalCollectionVC: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
4
5    var collectionView: UICollectionView!
6    let items = Array(1...20)
7
8    override func viewDidLoad() {
9        super.viewDidLoad()
10
11        let layout = UICollectionViewFlowLayout()
12        layout.scrollDirection = .horizontal
13        layout.minimumLineSpacing = 10
14        layout.minimumInteritemSpacing = 10
15        layout.sectionInset = UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
16
17        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
18        collectionView.dataSource = self
19        collectionView.delegate = self
20        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
21        collectionView.backgroundColor = .systemBackground
22
23        view.addSubview(collectionView)
24    }
25
26    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
27        return items.count
28    }
29
30    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
31        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
32        cell.backgroundColor = .systemBlue
33        return cell
34    }
35
36    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
37        return CGSize(width: 120, height: 120)
38    }
39}

1class CarouselVC: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
2
3    override func viewDidLoad() {
4        super.viewDidLoad()
5
6        let layout = UICollectionViewFlowLayout()
7        layout.scrollDirection = .horizontal
8        layout.minimumLineSpacing = 16
9
10        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
11        collectionView.translatesAutoresizingMaskIntoConstraints = false
12        collectionView.showsHorizontalScrollIndicator = false
13        collectionView.dataSource = self
14        collectionView.delegate = self
15        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
16
17        view.addSubview(collectionView)
18        NSLayoutConstraint.activate([
19            collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
20            collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
21            collectionView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
22            collectionView.heightAnchor.constraint(equalToConstant: 200),
23        ])
24    }
25
26    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
27        // Height matches collection view height minus insets for single row
28        return CGSize(width: 150, height: 180)
29    }
30
31    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { 10 }
32
33    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
34        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
35        cell.backgroundColor = .systemIndigo
36        cell.layer.cornerRadius = 12
37        return cell
38    }
39}

1let layout = UICollectionViewFlowLayout()
2layout.scrollDirection = .horizontal
3layout.minimumLineSpacing = 0
4
5let collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
6collectionView.isPagingEnabled = true
7collectionView.showsHorizontalScrollIndicator = false
8
9// Each item fills the entire visible area for full-page swiping
10func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
11    return collectionView.bounds.size
12}

1func createHorizontalLayout() -> UICollectionViewCompositionalLayout {
2    let itemSize = NSCollectionLayoutSize(
3        widthDimension: .fractionalWidth(1.0),
4        heightDimension: .fractionalHeight(1.0)
5    )
6    let item = NSCollectionLayoutItem(layoutSize: itemSize)
7    item.contentInsets = NSDirectionalEdgeInsets(top: 5, leading: 5, bottom: 5, trailing: 5)
8
9    let groupSize = NSCollectionLayoutSize(
10        widthDimension: .absolute(150),
11        heightDimension: .absolute(200)
12    )
13    let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])
14
15    let section = NSCollectionLayoutSection(group: group)
16    section.orthogonalScrollingBehavior = .continuous  // Horizontal scroll
17
18    return UICollectionViewCompositionalLayout(section: section)
19}
20
21// Usage
22let collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: createHorizontalLayout())

1// If using Interface Builder:
2// 1. Drag a UICollectionView onto the storyboard
3// 2. Select the Collection View
4// 3. In the Attributes Inspector, set "Scroll Direction" to "Horizontal"
5// 4. Adjust "Min Spacing" for line and item spacing
6
7// Or configure in code after outlet connection
8@IBOutlet weak var collectionView: UICollectionView!
9
10override func viewDidLoad() {
11    super.viewDidLoad()
12    if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
13        layout.scrollDirection = .horizontal
14    }
15}