Create multi-page PDFs async using SwiftUI layouts

CreatePDFView.swift

import SwiftUI
import PDFKit

let pdfRendererFormat = [
  kCGPDFContextCreator: "@mbotsu",
  kCGPDFContextAuthor: "@mbotsu",
  kCGPDFContextTitle: "Create multi-page PDFs with SwiftUI layouts",
  kCGPDFContextSubject: "Give up ImageRenderer and create PDFs with UIGraphicsPDFRenderer",
] as [String : Any]

struct CreatePDFView: View {
  @State var pdfUrl: URL?
  
  var body: some View {
    VStack {
      if let pdfUrl = pdfUrl {
        PdfFileView(url: pdfUrl)
      }
    }
    .onAppear {
      let views: [AnyView] = [
        AnyView(Page1()),
        AnyView(Page2()),
        AnyView(Page3()),
      ]
      Task {
        do {
          let url = try await createPdf("sample.pdf",
                                        options: pdfRendererFormat,
                                        views: views)
          pdfUrl = url
          print(url.path)
        } catch {
          print(error.localizedDescription)
        }
      }
    }
  }
  
  struct Page1: View {
    var body: some View {
      Text("Page1").font(.largeTitle)
    }
  }
  
  struct Page2: View {
    var body: some View {
      Text("Page2").font(.largeTitle)
    }
  }
  
  struct Page3: View {
    var body: some View {
      Text("Page3").font(.largeTitle)
    }
  }
}

func createUrl(fileName: String) throws -> URL {
  let fileManager = FileManager.default
  let url = fileManager.temporaryDirectory.appendingPathComponent(fileName, conformingTo: .pdf)
  if fileManager.fileExists(atPath: url.path) {
    try fileManager.removeItem(at: url)
  }
  return url
}

func createPdf(_ fileName: String, options: [String: Any],
               width:CGFloat=595.2, height:CGFloat=841.8,
               views: [AnyView]) throws -> URL {
  
  let format = UIGraphicsPDFRendererFormat()
  format.documentInfo = options
  
  let url = try createUrl(fileName: fileName)
  let pdfRect = CGRect(x: 0, y: 0, width: width, height: height)
  let pdfRenderer = UIGraphicsPDFRenderer(bounds: pdfRect, format: format)
  
  try pdfRenderer.writePDF(to: url , withActions: { context in
    views.forEach{ view in
      _createPdf(view, rect: pdfRect, context: context)
    }
  })
  
  return url
}

func _createPdf(_ view: AnyView, rect: CGRect,
                context: UIGraphicsPDFRendererContext){
  
  let vc = UIHostingController(rootView: view)
  vc.view.frame = rect
  vc.loadView()
  
  context.beginPage()
  context.cgContext.clear(rect)
  vc.view.drawHierarchy(in: rect, afterScreenUpdates: true)
  vc.removeFromParent()
  vc.view.removeFromSuperview()
}

struct PdfFileView : UIViewRepresentable {
  let url: URL
  
  func makeUIView(context: Context) -> some PDFView {
    let pdfView = PDFView()
    pdfView.document = PDFDocument(url: url)
    pdfView.autoScales = true
    pdfView.displayMode = .twoUpContinuous
    
    return pdfView
  }
  func updateUIView(_ uiView: UIViewType, context: Context) {}
}