fullScreenCoverを使用

サイドメニューがタブ等の下に表示されるので、fullScreenCoverを使って前面に表示する

swift

extension View {
    
    func sideMenu(isPresented: Binding<Bool>) -> some View {
        self.modifier(SideMenuView(isPresented: isPresented))
    }
}

swift

struct SideMenuView: ViewModifier {
    
    @Binding var isPresented: Bool
    @State var showSideMenu: Bool = false
    
    private let width: CGFloat = 270
    
    func body(content: Content) -> some View {
        content
            .fullScreenCover(isPresented: self.$isPresented) {
                let bounds = UIScreen.main.bounds
                let screenWidth = bounds.width
                ZStack {
                    GeometryReader { _ in EmptyView() }
                        .background(Color.gray.opacity(0.3))
                        .opacity(self.showSideMenu ? 1.0 : 0.0)
                        .opacity(1.0)
                        .animation(.easeIn(duration: 0.25), value: showSideMenu)
                        .onTapGesture {
                            self.showSideMenu = false
                        }
                    HStack {
                        VStack {
                            // TODO: リスト部分
                            Spacer()
                        }
                        .frame(width: width)
                        .background(.white)
                        .offset(x: self.showSideMenu ? screenWidth - self.width : screenWidth)
                        .animation(.easeIn(duration: 0.25), value: self.showSideMenu)
                        Spacer()
                    }
                }
                .background(BackgroundTranslucentView())
            }
            .onChange(of: self.isPresented) { _, newValue in
                if newValue {
                    DispatchQueue.main.async {
                        self.showSideMenu = true
                    }
                }
            }
            .onChange(of: self.showSideMenu) { _, newValue in
                if !newValue {
                    DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) {
                        var transaction = Transaction()
                        transaction.disablesAnimations = true
                        withTransaction(transaction) {
                            self.isPresented = false
                        }
                    }
                }
            }
    }
}

swift

struct BackgroundTranslucentView: UIViewRepresentable {
    
    func makeUIView(context: Context) -> UIView {
        let view = UIView()
        DispatchQueue.main.async {
            view.superview?.superview?.backgroundColor = .black.withAlphaComponent(0.2)
        }
        return view
    }

    func updateUIView(_ uiView: UIView, context: Context) {}
}

注意

isPresentedをtrueにする際はwithTransactionで囲んでfullScreenCoverのアニメーションをしないようにする