DiffableUI

DiffableUI is a set of wrappers and helpers built on top of UICollectionViewCompositionalLayout and UICollectionViewDiffableDataSource to help you write clean, reusable and SwiftUI-like code on the UIKit world.

How to use

To use DiffableUI, you must create a UIViewController that inherits from DiffableViewController, overwrite the sections computed variable and call reload() whenever you want the view to recompute, as such:

final class ExampleViewController: DiffableViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    reload()
  }

  @CollectionViewBuilder
  override var sections: [any CollectionSection] {
    List {
      Label("Hello DiffableUI!")
    }
  }
}

Customizing

The building blocks of DiffableUI are CollectionItem and CollectionSection. A CollectionItem represents any cell that you might want to display on your UICollectionView, while a CollectionSection holds your items and knows how to lay them out on the view.

Creating your own items is easy, you just have to provide an identifier, a way to hold your model, a reuse identifier and a way to configure your cell with your model:

public struct Empty: CollectionItem {
  public init() {}
  public var id: AnyHashable { item.id }
  public var item = EmptyHashable()
  public var reuseIdentifier: String { "empty" }
  public func configure(cell: UICollectionViewCell) {}

  public struct EmptyHashable: Hashable {
    let id = UUID()
  }
}

For a slightly more complex way of using DiffableUI, check our Hacker News example app, where we fetch the latest news and display them with a custom CollectionItem.

Extending

DiffableUI is built with SwiftUI-like extensibility in mind. Use the library's extensions to add functionality:

@CollectionViewBuilder
  override var sections: [any CollectionSection] {
    List {
      Label("Hello DiffableUI!")
      .onTap {
        print("Hello, console!")
      }
    }
  }

or create your own by extending CollectionItem or its concrete implementations themselves directly:

extension Label {
  func largeRedTitle() -> Self {
    self
      .fontStyle(.largeTitle)
      .textColor(.red)
  }
}

To create a new CollectionSection, you must provide an identifier, some way to hold [any CollectionItem] and provide a function that returns a NSCollectionLayoutSection. Check out List for more details.

Installation

You can add DiffableUI to your project by using Xcode's "Add Package Dependencies" option in the File menu, or add it as a dependency on your Package.swift file as:

dependencies: [
    .package(url: "https://github.com/loloop/DiffableUI",from: Version(0, 0, 1)),
  ],

Contributing and TODOs

To contribute, just open a pull request and let's take it from there :) Here's a couple of suggestions:

License

This library is released under the MIT license. See LICENSE for details.

loloop / DiffableUI