How to change a UICollectionViewListCell’s separator inset

In WWDC2020's session Lists in UICollectionView a slide is shown where a UICollectionViewListCell's separator inset is updated by assigning a new leading anchor to separatorLayoutGuide.leadingAnchor.

Unfortunately, this doesn't work in when you try to do it.

To set the separator inset for a UICollectionViewListCell you can update the leading anchor constraint by overriding updateConstraints in a UICollectionViewListCell subclass. Setting the anchor in init will cause the system to override your custom anchor leaving you with the default inset.

override func updateConstraints() {
  super.updateConstraints()

  separatorLayoutGuide.leadingAnchor.constraint(equalTo: someOtherView.leadingAnchor, constant: 10).isActive = true
}

You can set the leadingAnchor constraint just like you would set any other constraint. In fact, you can even set the separator's trailingAnchor using the same method I just showed if you want to offset the seperator from the trailing edge of your content view.