ASCollectionView

A SwiftUI implementation of UICollectionView & UITableView. Here's some of its useful features:

• supports preloading and onAppear/onDisappear.
• supports cell selection, with automatic support for SwiftUI editing mode.
• supports autosizing of cells.
• supports the new UICollectionViewCompositionalLayout, and any other UICollectionViewLayout
• supports removing separators for ASTableView.
• supports directly using FetchedResults as a data source

Getting Started

ASCollectionView is a swift package.

• It can be imported into an app project using Xcode’s new Swift Packages option, which is located within the File menu.
• When asked, use this repository's url: https://github.com/apptekstudios/ASCollectionView

Alternatively, if you're unable to use SPM for some reason, you can import it using cocoapods: pod 'ASCollectionView-SwiftUI', '~> 1.3'

Usage

Basic example - single section:

import ASCollectionView
import SwiftUI

struct SingleSectionExampleView: View {
	@State var dataExample = (0 ..< 30).map { $0 }
	
	var body: some View
	{
		ASCollectionView(data: dataExample, dataID: \.self) { item, _ in
			Color.blue
				.overlay(Text("\(item)"))
		}
		.layout {
			.grid(layoutMode: .adaptive(withMinItemSize: 100),
				  itemSpacing: 5,
				  lineSpacing: 5,
				  itemSize: .absolute(50))
		}
	}
}

Multiple sections with unique data sources

Below is an example of how to include a collection view with two sections (each with their own data source). For an extended example with a custom compositional layout see here. Or for more in-depth examples download the demo project included in this repo.

import SwiftUI
import ASCollectionView

struct ExampleView: View {
    @State var dataExampleA = (0 ..< 21).map { $0 }
    @State var dataExampleB = (0 ..< 15).map { "ITEM \($0)" }
    
    var body: some View
    {
        ASCollectionView
		{
			ASCollectionViewSection(
				id: 0,
				data: dataExampleA,
				dataID: \.self)
			{ item, _ in
				Color.blue
					.overlay(
						Text("\(item)")
					)
			}
			ASCollectionViewSection(
				id: 1,
				data: dataExampleB,
				dataID: \.self)
			{ item, _ in
				Color.green
					.overlay(
						Text("Complex layout - \(item)")
					)
			}
			.sectionHeader
			{
				HStack
				{
					Text("Section header")
						.padding()
					Spacer()
				}
				.background(Color.yellow)
			}
			.sectionFooter
			{
				Text("This is a section footer!")
					.padding()
			}
		}
		.layout { sectionID in
			switch sectionID {
				case 0:
				// Here we use one of the provided convenience layouts
				return .grid(layoutMode: .adaptive(withMinItemSize: 100),
							 itemSpacing: 5,
							 lineSpacing: 5,
							 itemSize: .absolute(50))
				default:
				return ASCollectionLayoutSection { environment in
					// ...
					// You could return any custom NSCollectionLayoutSection here. For an example see this file: /readmeAssets/SampleUsage.swift
					// ...
				}
			}
		}
	}
}

Supplementary Views

ASCollectionView has support for supplementary views. To add a supplementary view, use the sectionHeader, sectionFooter, or sectionSupplementary modifiers on your ASCollectionViewSection.

• sectionHeader and sectionFooter set the supplementary for UICollectionView.elementKindSectionHeader and UICollectionView.elementKindSectionHeader respectively.
• sectionSupplementary lets you specify any supplementaryKind.

ASCollectionViewSection(...) { ... }
	.sectionHeader
	{
		Text("Section header")
		.background(Color.yellow)
	}
	.sectionFooter
	{
		Text("Section footer")
		.background(Color.blue)
	}
        .sectionSupplementary(ofKind: "someOtherSupplementaryKindRequestedByYourLayout") {
                Text("Section supplementary")
		.background(Color.green)
        }

Decoration Views

A UICollectionViewLayout can layout decoration views that do not relate to the data (eg. a section background). These cannot be configured so you must provide a View struct that can be initialised using .init().

• To enforce this requirement, your view must conform to the Decoration protocol. The only requirement of this is an initialiser with no arguments.
• You must register the view type with the layout.
• See the Reminders screen of the Demo app for a working example.

Declaring a swift view conforming to Decoration:

struct GroupBackground: View, Decoration
{
	let cornerRadius: CGFloat = 12
	var body: some View
	{
		RoundedRectangle(cornerRadius: cornerRadius)
			.fill(Color(.secondarySystemGroupedBackground))
	}
}

Registering the decoration type with the layout (ASCollectionLayout):

var layout: ASCollectionLayout<Section>
{
	ASCollectionLayout<Section>
	{ 
            // ... Here is an example of including a decoration in a compositional layout.
            let sectionBackgroundDecoration = NSCollectionLayoutDecorationItem.background(elementKind: "groupBackground")
            sectionBackgroundDecoration.contentInsets = section.contentInsets
            section.decorationItems = [sectionBackgroundDecoration]
            // ...
}
.decorationView(GroupBackground.self, forDecorationViewOfKind: "groupBackground") //REGISTER the decoration view type

Layout

• There is inbuilt support for the new UICollectionViewCompositionalLayout.
  • You can define layout on a per-section basis, including the use of a switch statement if desired.
  • Work in progress: There are some useful methods that allow for easy definition of list and grid-based layouts (including orthogonal grids).

Define layout for all sections:

ASCollectionView(...) { ... }
.layout {
    ASCollectionLayoutSection { layoutEnvironment in
    	//Construct and return a NSCollectionLayoutSection here
    }
}

Define layout per section:

ASCollectionView(...) { ... }
.layout { sectionID in
    switch sectionID {
    case .userSection:
        return ASCollectionLayoutSection { layoutEnvironment in
            //Construct and return a NSCollectionLayoutSection here
        }
    }
    case .postSection:
        return ASCollectionLayoutSection { layoutEnvironment in
            //Construct and return a NSCollectionLayoutSection here
        }
    }
}

Use a custom UICollectionViewLayout:

ASCollectionView(...) { ... }
.layout {
    let someCustomLayout = CustomUICollectionViewLayout()
    someCustomLayout.estimatedItemSize = UICollectionViewFlowLayout.automaticSize
    return someCustomLayout
}

Other tips

• You can use an enum as your SectionID (rather than just an Int), this lets you easily determine the layout of each section.
• See the demo project for more in-depth usage examples.
• Please note that you should only use @State for transient visible state in collection view cells. Anything you want to persist long-term should be stored in your model.

Todo

See the open issues for a list of proposed features (and known issues).

GitHub