Framework to manage complex UICollectionView in declarative way and very few lines of code. Heavily inspired by https://github.com/maxsokolov/TableKit and https://github.com/Instagram/IGListKit

Development still in progress. Some changes may affect backward compatibility

Via CocoaPods: pod 'IVCollectionKit' Via Carthage github "ivedeneev/CollectionKit" Via Swift Package Manager: Coming soon

• Declarative UICollectionView management
• No need to implement UICollectionViewDataSource and UICollectionViewDelegate
• Easy way to map your models into cells
• Auto diffing
• Supports cells & reusable views from code and xibs and storyboard
• Flexible
• Register cells and reusable views automatically
• Fix scroll indicator clipping at iOS11 (http://www.openradar.me/34308893)

Key concepts of CollectionKit are Section, Item and Director. Item is responsible for UICollectionViewCell configuration, size and actions Section is responsible for group of items and provides information for each item, header/footer and all kind of insets/margins: section insets, minimum inter item spacing and line spacing Director is responsible for providing all information, needed for UICollectionView and its updations

Setup UICollectionView and director:

Setup collection view

collectionView = UICollectionView(frame: view.bounds, colletionViewLayout: UICollectionViewFlowLayout())
collectionDirector = CollectionDirector(colletionView: collectionView)

Create items

let item1 = CollectionItem<CollectionCell>(item: "hello!")
let item2 = CollectionItem<CollectionCell>(item: "im")
let item3 = CollectionItem<CollectionCell>(item: "ColletionKit")
let item4 = CollectionItem<ImageCell>(item: "greeting.png")

Create section and put items in section

let section = CollectionSection()
let items = [item1, item2, item3, item4]
section += items
director += section

Put section in director and reload director

director += section
director.reload()

Cell must implement ConfigurableCollectionCell protocol. You need to specify cell size and configuration methods:

extension CollectionCell : ConfigurableCollectionItem {
    static func estimatedSize(item: String, boundingSize: CGSize, in section: AbstractCollectionSection) -> CGSize {
        return CGSize(width: boundingSize.width - 40, height: 44)
    }

    func configure(item: String) {
        textLabel.text = item
    }
}

Note, that `contentInsets` value of collection view is respected in `boundingSize` parameter

Framework doesnt support auto-sizing cells, but you can adjust cell width and height to collection view dimensions

let item = CollectionItem<CollectionCell>(item: "text").adjustsWidth(true)

It means that width of this cell will be equal to collectionView.bounds.width minus collectionView content insets and section insets. width from estimatedSize method is ignored for this case. adjustsHeight(Bool) method has same logic, but for vertical insets.

Implement such actions like didSelectItem or shouldHighlightItem using functional syntax

let row = CollectionItem<CollectionCell>(item: "text")
    .onSelect({ (_) in
        print("i was tapped!")
    }).onDisplay({ (_) in
        print("i was displayed")
    })

Available actions:

• onSelect
• onDeselect
• onDisplay
• onEndDisplay
• onHighlight
• onUnighlight
• shouldHighlight

You can setup inter item spacing, line spacing and section insets using section object:

let section = CollectionSection()
section.minimumInterItemSpacing = 2
section.insetForSection = UIEdgeInsetsMake(0, 20, 0, 20)
section.lineSpacing = 2

Also you can set section header and footer:

section.headerItem = CollectionHeaderFooterView<SectionHeader>(item: "This is header")
section.footerItem = CollectionHeaderFooterView<SectionHeader>(item: "This is footer")

IVCollectionKit provides 2 ways for updatung UICollectionView content:

• reload (using reloadData)
• animated updates(using performBatchUpdates)

Note, that all models, that you use in CollectionItem initializations should conform Hashable protocol. Framework provides fallback for non-hashable models, but it may cause unexpected behaviour during animated updates.

director.performUpdates()
director.performUpdates { finished: Bool in
    print("updates completed")
}

If you need to animate cell size you can use `director.setNeedsUpdates()` method. This method doesnt trigger cell calculatuion under the hood

IMPORTANT! if you use animated updates via performUpdates or setNeedsUpdate dont use update methods of UICollectionView directly. It may lead to unpredictable behaviour

IVCollectionView is UICollectionView subclass designed to manage incorrect updates. You can use it instead of ordinary CollectionView. Typical use case is simultanious updates.

You can provide your own section implementation using AbstractCollectionSection protocol. For example, you can use it for using CollectionDirector with Realm.Results and save Results lazy behaviour or implementing expandable sections (see exapmles). Also you can create subclass of CollectionSection if you dont need radically different behaviour

If you need to implement UISrollViewDelegate methods for your collection view (e.g pagination support) you can use scrollDelegate property

final class ViewController: UIViewController, UIScrollViewDelegate {
    var director: CollectionDirector!
    ...
    
    private func setupDirector() {
        director.scrollDelegate = self
    }
}