SwiftUIの新機能

SwiftUIの新機能

SwiftUIに追加された最新の機能と、それらによってアプリをどのように改善できるかを確認しましょう。直接のディスクアクセスやスナップショットベースの差分処理により高性能なアプリの構築を可能にする新しいDocumentプロトコル、リスト／グリッド／セクションのコンテンツを並べ替えるための新しいAPI、表示の優先度設定や自動最小化の挙動などを実現するツールバーの機能強化を紹介します。拡張されたプレゼンテーションのためのAPI（任意のビューでのスワイプアクションなどの機能を追加）、AsyncImageのキャッシュの改善、Observable型の遅延状態初期化についても取り上げます。

関連する章
- 0:00 - Introduction
- 2:12 - Refreshed look and feel
- 8:06 - Document-based apps
- 15:18 - Presentation and interaction
- 19:58 - Data flow and performance
- 27:25 - Next steps
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- Code Along：SwiftUIによるパワフルなドラッグ＆ドロップ機能の構築
- UIKitアプリのモダナイズ

struct SidebarFooterView: View {
    @Environment(\.appearsActive) private var appearsActive

    var body: some View {
        MyAccountView()
            .opacity(appearsActive ? 1 : 0.5)
    }
}

3:34 - Menu icon visibility

CommandMenu("Stickers") {
    Button { openStore() } label: {
        Label("Store", systemImage: "bag.fill")
            .labelStyle(.titleAndIcon)
        }
    }
    // Other menu items
}

5:12 - Prominent tab role

TabView {
    Tab { EventsTab() }
    Tab { HolidaysTab() }
    Tab { FunTab() }

    Tab(role: .prominent) {
        CartTab()
    }
}

6:15 - Toolbar item visibility and overflow menu

// Toolbar item visibility priority

StickerPageView()
    .toolbar {
        ToolbarItemGroup {
            UndoButton()
            RedoButton()
        }
        .visibilityPriority(.high)
        ToolbarOverflowMenu {
            ChoosePhotoButton()
            ExportAsImageButton()
            ClearAllStickersButton()
        }
        ToolbarItem(placement: .topBarPinnedTrailing) {
            ShareButton()
        }
    }

7:37 - Minimize toolbar on scroll with toolbarMinimizeBehavior

// Minimize toolbar when scrolling

ScrollView {
    StickerListView()
}
.toolbarMinimizeBehavior(.onScrollDown, for: .navigationBar)

9:47 - Document creation sources with context parameter

// Use the context to create a document

@main
struct Stickers: App {
    var body: some Scene {
        DocumentGroupLaunchScene("Create a Sticker Page") {
            NewDocumentButton("New Sticker Page", source: .blank)
            NewDocumentButton("Sticker Page from Photo…", source: .photo)
        }
       
        DocumentGroup { /* ... */ }
    }
}
  
extension DocumentCreationSource {
    static let blank = Self(id: "blank")
    static let photo = Self(id: "photo")
}

10:01 - Use the context to create a document

@main
struct Stickers: App {
    var body: some Scene {
        DocumentGroupLaunchScene("Create a Sticker Page") {
            NewDocumentButton("New Sticker Page", source: .blank)
            NewDocumentButton("Sticker Page from Photo…", source: .photo)
        }
       
        DocumentGroup { document in
            StickerPageDocumentView(document)
        } { configuration, context in
            StickerPageDocument(configuration: configuration, context: context)
        }
    }
}

10:43 - Document app declaration

@main
struct Stickers: App {
    var body: some Scene {
        DocumentGroup { /* ... */ }
        WindowGroup { /* ... */ }
    }
}

11:25 - Implement document writing

@Observable
final class StickerDocument {
    // ...
}

11:34 - Implement document writing: list writable formats

@Observable
final class StickerDocument {
    
    static let writableDocumentTypes: [UTType] = [.stickerDocument]
  
    // ...
}

import UniformTypeIdentifiers

extension UTType {
    static let stickerDocument = UTType(exportedAs: "stickerdocument")
}

11:45 - Implement document writing: provide snapshot

@Observable
final class StickerDocument {
    
    static let writableDocumentTypes: [UTType] = [.stickerDocument]
  
    @MainActor
    func snapshot(contentType: UTType) async throws -> sending PageSnapshot { /* ... */ }
      
    // ...
}

11:54 - Implement document writing: represent the snapshot

struct PageSnapshot {
    var background: Image
    var metadata: StickerPlacements
    var stickers: [Image]
}

struct StickerPlacements { /* ... */ }

12:13 - Implement document writing: provide a DocumentWriter

@Observable
final class StickerDocument {
    
    static let writableDocumentTypes: [UTType] = [.stickerDocument]
  
    @MainActor
    func snapshot(contentType: UTType) async throws -> sending PageSnapshot {
        makeSnapshot()
    }
      
    func writer(configuration: sending WriteConfiguration) -> sending Writer {
        Writer(contentType: configuration.contentType)
    }
}

12:33 - DocumentWriter: Snapshot

struct Writer<Snapshot>: DocumentWriter {
    typealias Snapshot = PageSnapshot
    
    // ...
}

12:36 - DocumentWriter: PageSnapshot as Snapshot

struct Writer<Snapshot>: DocumentWriter {
    typealias Snapshot = PageSnapshot
  
    let contentType: UTType
    
    // ...
}

12:42 - DocumentWriter protocol implementation

struct Writer<Snapshot>: DocumentWriter {
    typealias Snapshot = PageSnapshot
  
    let contentType: UTType
    
    nonisolated func write(
        snapshot: sending PageSnapshot, to destination: URL,
        previous: sending PageSnapshot?, progress: consuming Subprogress
    ) async throws {
        // write .stickerDocument
    }
}

13:18 - Progress reporting during writing

struct Writer<Snapshot>: DocumentWriter {
    typealias Snapshot = PageSnapshot
  
    let contentType: UTType
    
    nonisolated func write(
        snapshot: sending PageSnapshot, to destination: URL,
        previous: sending PageSnapshot?, progress: consuming Subprogress
    ) async throws {
        // report progress…
        // write .stickerDocument
    }
}

13:27 - Implement document reading with ReadableDocument protocol
```
extension StickerDocument: ReadableDocument {
  
}
```

14:35 - Add PNG to supported formats list

@Observable
final class StickerDocument: WritableDocument {
  
    static let writableContentTypes: [UTType] = [.stickerDocument, .png]
}

14:48 - Add content type checks

struct Writer<Snapshot>: DocumentWriter {
    typealias Snapshot = PageSnapshot
  
    let contentType: UTType
    
    nonisolated func write(
        snapshot: sending PageSnapshot, to destination: URL,
        previous: sending PageSnapshot?, progress: consuming Subprogress
    ) async throws {
        if contentType.conforms(to: .stickerDocument) {
            // write .stickerDocument
        } else if contentType.conforms(to: .png)
        
    }
}

14:56 - Writing multiple formats including PNG

struct Writer<Snapshot>: DocumentWriter {
    typealias Snapshot = PageSnapshot

    let contentType: UTType

    nonisolated func write(
        snapshot: sending PageSnapshot, to destination: URL, 
        previous: sending PageSnapshot?, progress: consuming Subprogress
    ) async throws {
        if contentType.conforms(to: .stickerDocument) {  
            // write .stickerDocument
        } else if contentType.conforms(to: .png) {
            let context = CGContext(/* ... */) 
            context.draw(/* ... */)
        }
    }
}

15:58 - Reorderable list with reorderContainer

List {
    ForEach(stickers) { sticker in
        StickerListItemView(sticker: sticker)
    }
    .reorderable()
}
.reorderContainer(for: Sticker.self) { difference in
    difference.apply(to: &stickers)
}

16:14 - Apply changes to a reorderable list's data source

import OrderedCollections // from https://github.com/apple/swift-collections

extension ReorderDifference where CollectionID == ReorderableSingleCollectionIdentifier {
    func apply(to values: inout [some Identifiable<ItemID>]) {
        var dictionary = OrderedDictionary(uniqueKeys: values.map { $0.id }, values: values)
        let destinationOffset: Int? = switch destination.position {
        case .before(let destination):
            dictionary.keys.firstIndex(of: destination)
        case .end:
            nil
        }
        dictionary.move(keys: sources, to: destinationOffset ?? values.endIndex)
        values = dictionary.values.elements
    }
}

16:48 - Reorderable grid with LazyVGrid

LazyVGrid {
    ForEach(stickers) { sticker in
        StickerListItemView(sticker: sticker)
    }
    .reorderable()
}
.reorderContainer(for: Sticker.self) { difference in
    difference.apply(to: &stickers)
}

18:12 - Swipe actions on List

List {
    ForEach(stickers) { sticker in
        StickerListItemView(sticker: sticker)
            .swipeActions {
                DeleteButton(sticker: sticker)
            }
    }
}

18:15 - Swipe actions on any view

ScrollView {
    LazyVStack {
        ForEach(stickers) { sticker in
            StickerListItemView(sticker: sticker)
                .swipeActions {
                    DeleteButton(sticker: sticker)
                }
        }
    }
}
.swipeActionsContainer()

18:54 - Confirmation dialog with item binding

struct StickerCanvasView: View {
    var stickers: [Sticker]
    @State private var stickerToDelete: Sticker?

    var body: some View {
        ZStack {
            ForEach(stickers) { sticker in
                PlacedStickerView(sticker: sticker)
                    .contextMenu {
                        // ...
                    }
            }
        }
        .confirmationDialog(
            "Delete?", item: $stickerToDelete
        ) { sticker in
            DeleteStickerButton(sticker)
        }   
    }
}

19:35 - Alert with item binding

struct StickerCanvasView: View {
    var stickers: [Sticker]
    @State private var stickerToDelete: Sticker?

    var body: some View {
        ZStack {
            ForEach(stickers) { sticker in
                PlacedStickerView(sticker: sticker)
                    .contextMenu {
                        // ...
                    }
            }
        }
        .alert(
            "Delete?", item: $stickerToDelete
        ) { sticker in
            DeleteStickerButton(sticker)
        }   
    }
}

21:18 - AsyncImage with URLRequest and custom URLSession

@Observable class StickerStore {
    static let imageSession: URLSession = {
        let config = URLSessionConfiguration.default
        config.urlCache = URLCache(
            memoryCapacity: 64 * 1024 * 1024,
            diskCapacity: 256 * 1024 * 1024)
        return URLSession(configuration: config)
    }()
}

ForEach(pets) { pet in
    AsyncImage(request: URLRequest(
        url: pet.imageURL,
        cachePolicy: .returnCacheDataElseLoad)
    )
}
.asyncImageURLSession(StickerStore.imageSession)

23:08 - @State converted to macro for lazy initialization

@Observable class StickerStore { }

struct StickerStoreView: View {
    // store is now lazily initialized, only
    // created once for the lifetime of the view
    @State private var store = StickerStore()

    var body: some View {
        // ...
    }
}

23:48 - @State macro init assignment error

struct StickerPageView: View {
    @State private var page = StickerPage()
    let title: String
    
    init(title: String) {
        self.page = StickerPage(title: title) // Variable 'self.title' used before being initialized
        self.title = title
    }
    
    var body: some View {
        // ...
    }
}

24:02 - Fixed @State macro init assignment error

struct StickerPageView: View {
    @State private var page: StickerPage // Removed default value to fix error
    let title: String
    
    init(title: String) {
        self.page = StickerPage(title: title)
        self.title = title
    }
    
    var body: some View {
        // ...
    }
}

26:07 - @ContentBuilder

@ContentBuilder
func stickerLibraryView() -> some View {
  // ...
}

- 0:00 - Introduction
- This video covers the refreshed Liquid Glass look and feel, new document-based app APIs, presentation and interaction improvements, and data flow and performance enhancements.
- 2:12 - Refreshed look and feel
- Apps automatically adopt the updated Liquid Glass appearance on 2027 OS releases without code changes. Covers interactive Liquid Glass elements, the inactive window appearance on iPadOS, toolbar customization with overflow menus and pinned placements, minimize-on-scroll behavior, and guidance for building resizable apps using size classes.
- 8:06 - Document-based apps
- Expanded document APIs for SwiftUI apps, including the new DocumentCreationSource API for custom new-document flows, performance improvements for reading and writing large documents, and first-class support for direct document URL access via the FileDocument and ReferenceFileDocument protocols.
- 15:18 - Presentation and interaction
- New reorderable container APIs let users drag to reorder items in any container — List, LazyVGrid, and on watchOS for the first time. Also covers swipe actions on arbitrary views beyond List, and item binding-driven confirmation dialogs.
- 19:58 - Data flow and performance
- AsyncImage now supports standard HTTP caching by default, with new APIs for custom URLRequest and URLSession configurations. The @State property wrapper is converted to a macro, making class initialization lazy to prevent redundant allocations — back-ported to iOS 17, macOS 14, and aligned releases.
- 27:25 - Next steps
- Key takeaways and recommended next steps: build in Xcode 27 to see the updated Liquid Glass look in your app, adopt the new Document APIs for document-based apps, and explore the SwiftUI agent skills.

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