list_view.md

Managing collection views

Basic concepts

Instead of direct UICollectionView usage, ALLKit provides smart abstraction over:

let adapter = CollectionViewAdapter<...>(layout: /* collectionViewLayout */)

Adapter is a collection view data source (delegate is up to you) and manages cells using yoga layout.

All you need is just pass bouding dimensions:

adapter.collectionView.frame = view.bounds

adapter.set(
    boundingDimensions: CGSize(...).layoutDimensions
)

and data items:

let items: [ListItem<...>] = ...

adapter.set(items: items, animated: true)

That's it. And no direct calls of performBatchUpdates or reloadData.

ListItem object represents cell and connects data model with UI:

let item = ListItem<...>(id: Hashable, layoutSpec: LayoutSpec)

ID is needed to calculate the changes between the previous and current item lists.

Swipe actions

UICollectionView does not have built-in swiping support, like UITableView. With ALLKit, you can easily set up swipe actions (available by Extended subspec):

let actions = SwipeActions(...)

item.makeView = { layout, index -> UIView in
    actions.makeView(contentLayout: layout)
}

Different sizes

In complex lists, items can have different sizes — a full-width header, a multi-column grid, etc. For this purpose, ListItem has a special property:

item.boundingDimensionsModifier = { w, h in
    return (w / 2, .nan)
}

Interactive movement

To enable this feature, you need to configure both the adapter and the elements:

adapter.settings.allowInteractiveMovement = true

adapter.collectionView.all_addGestureRecognizer { [weak self] (g: UILongPressGestureRecognizer) in
    self?.adapter.handleMoveGesture(g)
}
...

item.canMove = true
item.didMove = { from, to in }

Custom collection view and cells

In most cases, this feature is not used. But sometimes, for example, if you want to override cell layout attributes, it can be useful:

final class CustomCell: UICollectionViewCell {
    override func apply(_ layoutAttributes: UICollectionViewLayoutAttributes) {
        super.apply(layoutAttributes)

        ...
    }
}

...

let adapter = CollectionViewAdapter<UICollectionView, CustomCell, Any>()

❗️❗️❗️ DO NOT ❗️❗️❗️

• ...modify cell's contentView directly. Adapter creates cell UI based on the spec that you specified in the ListItem object.
• ...call collection view methods that are relevant to updating UI, such as reloadData, performBatchUpdates, etc. May the AutoDiff be with you.
• ...setting the collection view dataSource.
• ...enable prefetching in collection view.