PagingView by working with SwiftUI internals. Useful for building "flat" view containers, like a paging view! The paging view itself uses yet another internal type. But serves as a good example for how to build a useful view.

Example.swift

import SwiftUI

struct ContentView: View {
  @State
  private var show = false

  @State
  private var selection = 0

  var body: some View {
    PagingView(page: $selection) {
      Color.red.overlay {
        VStack(spacing: 15) {
          Button("Go next") {
            selection = 1
          }
          Button("Go next animated") {
            withAnimation {
              selection = 1
            }
          }
        }
      }
      Color.green.overlay {
        Button("Toggle 3rd view.") {
          show.toggle()
        }
      }
      if show {
        Color.blue
      }
    }
    .ignoresSafeArea()
    .tint(.white)
    .overlay(alignment: .bottom) {
      Text(selection, format: .number)
        .frame(maxWidth: .infinity)
        .padding()
        .background(.thinMaterial)
    }
  }
}

PagingView.swift

public struct PagingView<Views: View>: View {
  public typealias Config = _PagingViewConfig
  public typealias PageIndex = _VariadicView.Children.Index

  private let tree: _VariadicView.Tree<Root, Views>

  public init(
    config: Config = Config(),
    page: Binding<PageIndex>? = nil,
    @ViewBuilder _ content: () -> Views
  ) {
    tree = _VariadicView.Tree(
      Root(
        config: config,
        page: page
      ),
      content: content
    )
  }

  public var body: some View { tree }

  struct Root: _VariadicView.UnaryViewRoot {
    let config: Config
    let page: Binding<PageIndex>?

    func body(children: _VariadicView.Children) -> some View {
      _PagingView(
        config: config,
        page: page,
        views: children
      )
    }
  }
}