I found this modification that takes into account the velocity as well as the bestSnappingLayout:
return super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity)
}
var offsetAdjusment = CGFloat.greatestFiniteMagnitude
let horizontalCenter = proposedContentOffset.x + (collectionView.bounds.width / 2)
let targetRect = CGRect(x: proposedContentOffset.x, y: 0, width: collectionView.bounds.size.width, height: collectionView.bounds.size.height)
let layoutAttributesArray = super.layoutAttributesForElements(in: targetRect)
layoutAttributesArray?.forEach({ (layoutAttributes) in
let itemHorizontalCenter = layoutAttributes.center.x
if abs(itemHorizontalCenter - horizontalCenter) < abs(offsetAdjusment) {
if abs(velocity.x) < 0.3 { // minimum velocityX to trigger the snapping effect
offsetAdjusment = itemHorizontalCenter - horizontalCenter
} else if velocity.x > 0 {
offsetAdjusment = itemHorizontalCenter - horizontalCenter + layoutAttributes.bounds.width
} else { // velocity.x < 0
offsetAdjusment = itemHorizontalCenter - horizontalCenter - layoutAttributes.bounds.width
}
}
})
return CGPoint(x: proposedContentOffset.x + offsetAdjusment, y: proposedContentOffset.y)
}