Discover sncf-connect-tech/Collor Open Source project

About

Collor is a MVVM data-oriented framework for accelerating, simplifying and ensuring UICollectionView building.
Collor was created for and improved in the Voyages-sncf.com app.

Features

Here is the list of all the features:

Getting started

A medium article which explains the purpose and how to use Collor.
Another medium article to understand the diffing feature.
How to create your own API above UICollectionView with Collor

Example

To run the example project, clone the repo, and run pod install from the Example directory first.
There are 4 examples:

Menu : Simple collectionView with userEvent propagation example
Random : Diffing entire data + custom layout
Weather : Diffing sections + custom layout
Pantone : Adding and remove items using CollectionDatas.
RealTime : Complex diffing (insert, delete, reload) + custom layout handling with DecorationViewHandler.
Alphabet : An example with a supplementaryView + custom layout handling with SupplementaryViewsHandler.

Usage

The UICollectionView is represented by a collectionData object which contains sectionDescriptors which contain themself cellDescriptors. Each item or cell in Collor is composed by 3 objects:

The UICollectionViewCell (XIB or not + swift file) which implements CollectionCellAdaptable
A cellDescriptor which implements CollectionCellDescribable
An adapter (view model) which implements CollectionAdapter

CellDescriptor

It describes the cell and is the link between the cell and the viewModel. Logically, one type of cell needs only one cellDescriptor. It owns the cell identifier, the cell className and handles the size of the cell. The collectionData handles cell registering and dequeuing using these properties.

final class WeatherDayDescriptor: CollectionCellDescribable {

    let identifier: String = "WeatherDayCollectionViewCell"
    let className: String = "WeatherDayCollectionViewCell"
    var selectable:Bool = false

    let adapter: WeatherDayAdapter

    init(adapter: WeatherDayAdapter) {
        self.adapter = adapter
    }

    func size(_ collectionView: UICollectionView, sectionDescriptor: CollectionSectionDescribable) -> CGSize {
        let sectionInset = sectionDescriptor.sectionInset(collectionView)
        let width:CGFloat = collectionView.bounds.width - sectionInset.left - sectionInset.right
        return CGSize(width:width, height:60)
    }

    public func getAdapter() -> CollectionAdapter {
        return adapter
    }
}

Adapter

An adapter is a viewModel object. It transforms your model in a human readable data used by the cell.

struct WeatherDayAdapter: CollectionAdapter {

    let date: NSAttributedString

    static let dateFormatter: DateFormatter = {
        let df = DateFormatter()
        df.dateFormat = "EEEE d MMMM"
        return df
    }()

    init(day:WeatherDay) {

        let dateString = WeatherDayAdapter.dateFormatter.string(from: day.date)
        date = NSAttributedString(string: dateString, attributes: [
            NSFontAttributeName: UIFont.boldSystemFont(ofSize: 18),
            NSForegroundColorAttributeName: UIColor.black
        ])
    }
}

When a cell is dequeued, the collectionData updates the cell with this object.

final class WeatherDayCollectionViewCell: UICollectionViewCell, CollectionCellAdaptable {
  @IBOutlet weak var label: UILabel!

  func update(with adapter: CollectionAdapter) {
        guard let adapter = adapter as? WeatherDayAdapter else {
            fatalError("WeatherDayAdapter required")
        }
        label.attributedText = adapter.date
    }
}

ViewController

Create the dataSource and the delegate:

lazy var collectionViewDelegate: CollectionDelegate = CollectionDelegate(delegate: self)
lazy var collectionViewDatasource: CollectionDataSource = CollectionDataSource(delegate: self)

Create the collectionData:

let collectionData = MyCollectionData()

Bind the collectionView with the data, the datasource and the delegate:

bind(collectionView: collectionView, with: collectionData, and: collectionViewDelegate, and: collectionViewDatasource)

Create a section and one cell in the collectionData:

final class MyCollectionData : CollectionData {

    override func reloadData() {
        super.reloadData()

        let section = MySectionDescriptor().reloadSection { (cells) in
                let cell = MyColorDescriptor(adapter: MyColorAdapter(model: "someThing"))
                cells.append(cell)
            })
        }
        sections.append(section)
    }
}

MySectionDescriptor:

final class MySectionDescriptor : CollectionSectionDescribable {

  func sectionInset(_ collectionView: UICollectionView) -> UIEdgeInsets {
      return UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10)
  }
}

You get a readable data which represents your UICollectionView, without code duplication, reusing cell and with a good separation of code.

SupplementatyView

To add a supplementaryView, instead of using CollectionSectionDescribable.reloadSection(:), call CollectionSectionDescribable.reload(:). The builder passed as parameter exposes new method to add a supplementaryView easily.

let section = MySectionDescriptor().reload { builder in
    let letterAdapter = LetterAdapter(letter: "A")
    let letterDescriptor = LetterCollectionReusableViewDescriptor(adapter: letterAdapter)
    builder.add(supplementaryView: letterDescriptor, kind: "letter")
}
sections.append(section)

CollectionSupplementaryViewDescribable behaves like a CollectionCellDescribable. It needs an adapter to fill the view with data. But, for displaying a supplementaryView correctly, a custom layout is required in order to set attributes for the supplementaryViews created in the CollectionData. As with decorationViews, Collor provides a SupplementaryViewsHandler` object to manage supplementaryViews. It handles addition, caching and updatating.

class Layout : UICollectionViewFlowLayout {
    //...
    override func prepare() {
        super.prepare()
        
        supplementaryViewsHandler.prepare()
        
        for (sectionIndex, sectionDescriptor) in datas.sections.enumerated() {
            
            let firstCellIndexPath = IndexPath(item: 0, section: sectionIndex)
            let firstCellAttributes = layoutAttributesForItem(at: firstCellIndexPath)!
            
            sectionDescriptor.supplementaryViews.forEach { (kind, views) in
                
                views.enumerated().forEach { (index, viewDescriptor) in
                    let indexPath = IndexPath(item: index, section: sectionIndex)
                    let a = UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: kind, with: indexPath)
                    a.frame = viewDescriptor.frame(collectionView, sectionDescriptor: sectionDescriptor)
                    a.frame.origin.y += firstCellAttributes.frame.origin.y
                    
                    supplementaryViewsHandler.add(attributes: a)
                }
            }
        }
    }
    
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        let attributes = super.layoutAttributesForElements(in: rect)
        let supplementaryAttributes = supplementaryViewsHandler.attributes(in: rect)
        if let attributes = attributes {
            return attributes + supplementaryAttributes
        }
        return attributes
    }
    
    override func layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        return supplementaryViewsHandler.attributes(for: elementKind, at: indexPath)
    }
    
    override func prepare(forCollectionViewUpdates updateItems: [UICollectionViewUpdateItem]) {
        super.prepare(forCollectionViewUpdates: updateItems)
        supplementaryViewsHandler.prepare(forCollectionViewUpdates: updateItems)
    }
    
    override func indexPathsToInsertForSupplementaryView(ofKind elementKind: String) -> [IndexPath] {
        return supplementaryViewsHandler.inserted(for: elementKind)
    }
    
    override func indexPathsToDeleteForSupplementaryView(ofKind elementKind: String) -> [IndexPath] {
        return supplementaryViewsHandler.deleted(for: elementKind)
    }
}

Diffing and updating

Collor provides some features to easily update your collectionData.

Updating

Just append or remove cells or sections using CollectionData.update(_:) method. This means an end to fiddling around with IndexPath:

let newCellDescriptor = NewCellDescriptor(...)
let result = collectionData.update { updater in
    updater.append(cells: [newCellDescriptor], after: anotherCellDescriptor)
}
collectionView.performUpdates(with: result)

Here is the list of all update methods available:

append(cells:after:)
append(cells:before:)
append(cells:in:)
remove(cells:)
reload(cells:)
append(sections:after:)
append(sections:before:)
append(sections:)
remove(sections:)
reload(sections:)

Diffing

Collor is using a home made algorithm for getting the "diff" between two updates of your collectionData.

Diffing some sections:

sectionDescriptor.isExpanded = !sectionDescriptor.isExpanded
let result = collectionData.update{ updater in
    updater.diff(sections: [sectionDescriptor])
}
collectionView.performUpdates(with: result)

Diffing entire data

model.someUpdates()
let result = collectionData.update { updater in
    collectionData.reload(model: model)
    updater.diff()
}
collectionView.performUpdates(with: result)

Effortless management of decoration views

With DecorationViewHandler, you no longer need to implement code to manage your decoration views:

// register decoration view or class:
decorationViewHandler.register(viewClass: SimpleDecorationView.self, for: sectionBackgroundKind)
// caching
decorationViewHandler.add(attributes: backgroundAttributes)
// compute elements in rect
decorationViewHandler.attributes(in:rect)
// retrieving
decorationViewHandler.attributes(for: elementKind, at: atIndexPath)
// update handling
decorationViewHandler.prepare(forCollectionViewUpdates: updateItems)
return decorationViewHandler.inserted(for: elementKind)
return decorationViewHandler.deleted(for: elementKind)

For more information, have a look at this medium article.

XCTemplates

Collor is published with 3 xctemplates for helping you creating ViewController, SectionDescriptor and CellDescriptor.

To install them, just go in xctemplates directory and run this command in a terminal:

sh install.sh

Requirements

iOS 10.0+
Swift 4.2+ (get the 1.0.3 release for swift3.x, 1.1.23 for swift4.0)
Xcode 10.1+

Installation

CocoaPods

Collor is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "Collor"

Carthage

Collor doesn't yet support Carthage. Work in progress...

Documentation

Work in progress... 1% documented

Credits

Collor is owned and maintained by oui.sncf.

Collor was originally created by Gwenn Guihal.

License

Collor is available under the BSD license. See the LICENSE file for more info.

sncf-connect-tech/Collor

sncf-connect-tech

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