What's New in SwiftUI (iOS 27)

import SwiftUI
import UniformTypeIdentifiers

// MARK: - Document Model

struct PageSnapshot {
    let text: String
    let timestamp: Date
}

@Observable
final class NoteDocument: WritableDocument, ReadableDocument {
    var text: String = ""

    // MARK: WritableDocument
    static var writableContentTypes: [UTType] { [.plainText] }

    func snapshot() throws -> PageSnapshot {
        PageSnapshot(text: text, timestamp: Date())
    }

    func makeWriter() -> some DocumentWriter<PageSnapshot> {
        NoteWriter()
    }

    // MARK: ReadableDocument
    static var readableContentTypes: [UTType] { [.plainText] }

    func apply(_ snapshot: PageSnapshot) {
        text = snapshot.text
    }

    func makeReader() -> some DocumentReader<PageSnapshot> {
        NoteReader()
    }
}

struct NoteWriter: DocumentWriter {
    typealias Snapshot = PageSnapshot

    nonisolated func write(
        _ snapshot: PageSnapshot,
        to url: URL,
        previousSnapshot: PageSnapshot?,
        progress: Foundation.Progress
    ) async throws {
        // Only write if content actually changed
        guard snapshot.text != previousSnapshot?.text else {
            progress.completedUnitCount = 1
            return
        }
        let data = Data(snapshot.text.utf8)
        try data.write(to: url, options: .atomic)
        progress.completedUnitCount = 1
    }
}

struct NoteReader: DocumentReader {
    typealias Snapshot = PageSnapshot

    nonisolated func read(from url: URL) async throws -> PageSnapshot {
        let data = try Data(contentsOf: url)
        let text = String(decoding: data, as: UTF8.self)
        return PageSnapshot(text: text, timestamp: Date())
    }
}

// MARK: - App Entry Point

@main
struct NoteApp: App {
    var body: some Scene {
        DocumentGroup(newDocument: NoteDocument()) { file in
            NoteEditorView(document: file.document)
        }
    }
}

// MARK: - Editor View with New Toolbar APIs

struct NoteEditorView: View {
    @Bindable var document: NoteDocument

    var body: some View {
        ScrollView {
            TextEditor(text: $document.text)
                .padding()
        }
        // Scroll down hides the nav bar to reclaim space
        .toolbarMinimizeBehavior(.onScrollDown, for: .navigationBar)
        .toolbar {
            // High-priority group: always visible
            ToolbarItemGroup(placement: .topBarLeading) {
                Button("Undo", systemImage: "arrow.uturn.backward") {}
                Button("Redo", systemImage: "arrow.uturn.forward") {}
            }
            .visibilityPriority(.high)

            // Always pinned to trailing edge
            ToolbarItem(placement: .topBarPinnedTrailing) {
                ShareLink(item: document.text)
            }

            // Lower-priority actions go into overflow menu
            ToolbarOverflowMenu {
                Button("Export as PDF", systemImage: "doc.richtext") {}
                Button("Clear All", systemImage: "trash", role: .destructive) {}
            }
        }
        .navigationTitle("My Note")
    }
}