The CarouselLayoutGenerator struct provides a convenient way to generate a UICollectionViewCompositionalLayout with a carousel-style layout.

CarouselLayoutGenerator.swift

import UIKit

/// The CarouselLayoutGenerator struct provides a convenient way to generate a UICollectionViewCompositionalLayout with a carousel-style layout.
/// This layout is suitable for creating horizontally scrolling carousels of items, commonly used in applications to showcase a series of items or images.
///
/// Example:
/// ```
/// +----------------------------+
/// | ______________________ ____|_________________ ______________________
/// | |                    | |   |                | |                    |
/// | |       Cell1        | |   |   Cell2        | |       Cell         |
/// | |                    | |   |                | |                    |
/// | |                    | |   |                | |                    |
/// | ---------------------- ----|----------------- ----------------------
/// +----------------------------+
/// ```
///
public enum CarouselLayoutGenerator {
    /// Creates and returns an NSCollectionLayoutSection configured for a carousel layout.
    ///
    /// The section consists of a single group with horizontally arranged items.
    /// Each item spans the full width of the collection view and has a height based on a specified aspect ratio.
    ///
    /// - Returns: An NSCollectionLayoutSection configured for a carousel layout.
    public static func carouselSection() -> NSCollectionLayoutSection {
        let item = NSCollectionLayoutItem(
            layoutSize: .init(
                widthDimension: .fractionalWidth(1),
                heightDimension: .fractionalHeight(1)
            )
        )
        let group = NSCollectionLayoutGroup.horizontal(
            layoutSize: .init(
                // Aspect ratio: cell width ± insets / total width ± insets
                // Set cell width based on cell height
                widthDimension: .fractionalHeight(1.92),
                heightDimension: .fractionalHeight(1)
            ),
            subitems: [item]
        )
        let section = NSCollectionLayoutSection(group: group)
        section.orthogonalScrollingBehavior = .groupPaging
        section.interGroupSpacing = 8
        section.contentInsets = .init(top: 8, leading: 8, bottom: 8, trailing: 8)
        return section
    }

    /// Creates and returns a UICollectionViewCompositionalLayout with a single section using the carousel layout.
    ///
    /// - Returns: A UICollectionViewCompositionalLayout configured with the carousel layout.
    public static func create() -> UICollectionViewCompositionalLayout {
        UICollectionViewCompositionalLayout(section: carouselSection())
    }
}