Auto Sizing Cells

UICollectionReusableView+handlePreferredLayoutAttributesFitting.swift

import UIKit

extension UICollectionReusableView {
    /**
     Used for creating dynamic height cells
     
     - Call from overridden UICollectionReusableView (Cell) method `preferredLayoutAttributesFitting(_:)` which the system calls
     - Setup the cell width in `sizeForItem` as usual & pass a temp height
     - Setup Autolayout on cells to ensure a height can be computed
     
     - Parameter UICollectionViewLayoutAttributes: pass from overridden method
     
     - Returns: `UICollectionViewLayoutAttributes`
     */
    func handlePreferredLayoutAttributesFitting(
        _ layoutAttributes: UICollectionViewLayoutAttributes
    ) -> UICollectionViewLayoutAttributes {
        setNeedsLayout()
        layoutIfNeeded()
        // should work on both headers/footers and plain cells
        let v = (self as? UICollectionViewCell)?.contentView ?? self
        let size = v.systemLayoutSizeFitting(layoutAttributes.size)
        var newFrame = layoutAttributes.frame
        newFrame.size.height = ceil(size.height)
        layoutAttributes.frame = newFrame
        return layoutAttributes
    }
    
    /*
    I also set this (but probably isn't required)
    layout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
    */
    
    extension OrderDetailsViewController: UICollectionViewDelegateFlowLayout {
    func collectionView(
        _ collectionView: UICollectionView,
        layout collectionViewLayout: UICollectionViewLayout,
        sizeForItemAt indexPath: IndexPath
    ) -> CGSize {
        // 100 height is just a temporary value
        .init(width: collectionView.bounds.width, height: 100)
    }
}
}