Prioritize spacing over size for UICollectionViewCell

Question

I have a UICollectionView for which I want 3 cells in each row. I want to have a fixed spacing between each cell, with the size of the cell dynamically adjusting.

Yes, I am able to set min cell spacing. However I want this spacing to be fixed. How can I set the spacing between cells to be constant while the cells size adjust?

Answer 1

Here is how I solved it:

extension ViewController: UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        //Calculate cell width
        let spacingTotal = CGFloat((cellSpacing * 2) + (marginSpacing * 2))
        let screenWidth = UIScreen.main.bounds.width
        let cellWidth = (screenWidth - spacingTotal) / 3.0

        //Maintain ratio for cell height
        let widthToHeighRatio = CGFloat(102 / 94)
        let cellHeight = cellWidth * widthToHeighRatio

        return CGSize(width: cellWidth, height: cellHeight)
    }
}

Where cellSpacing is the value of your minimum cell spacing. And margingSpacing is the total value of your right and left margins for the collectionView.

Also note I'm maintaining a ratio for the cell size; the designs I'm working with display a 102 x 94 cell, so I'm maintaining that ratio for every screen size.

Here's how it looks on an iPhone SE and iPhone X: