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

Pull requests and suggestions welcome :)

Report Bug · Suggest a feature

Getting Started
Usage
Todo
License

Screenshots from demo app

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

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).

License

Distributed under the MIT License. See LICENSE for more information.

alexandrethsilva/ASCollectionView