Create and combine PDFs of SwiftUI layouts

PDFCombineView.swift

import SwiftUI
import PDFKit

let pdfDocumentOptions = [
    kCGPDFContextCreator: "@mbotsu",
    kCGPDFContextAuthor: "@mbotsu",
    kCGPDFContextTitle: "Create and combine PDFs with SwiftUI layouts",
    kCGPDFContextSubject: "Give up ImageRenderer and create PDFs with UIGraphicsPDFRenderer",
] as [PDFDocumentWriteOption : Any]

struct PDFCombineView: View {
  @State var pdfDocument: PDFDocument?
  
  var body: some View {
    VStack {
      if let pdfDocument = pdfDocument {
        PdfView(pdfDocument: pdfDocument)
      }
    }
    .onAppear {
      do {
        let pdfData1 = Page1().toPdfData()
        let pdfData2 = Page2().toPdfData()
        let pdfData3 = Page3().toPdfData()
        
        if let document = combinePdf(pdfData1, pdfData2, pdfData3){
          pdfDocument = document
          let url = try write("sample.pdf", pdfDocument: document, options: pdfDocumentOptions)
          print(url.path)
        } else {
          throw NSError(domain: "combine failed", code: -1)
        }
      } catch {
        print(error.localizedDescription)
      }
    }
  }
  
  func write(_ fileName: String, pdfDocument: PDFDocument, options: [PDFDocumentWriteOption : Any]) throws -> URL {
    let url = try createUrl(fileName: fileName)
    pdfDocument.write(to: url, withOptions: options)
    return url
  }
  
  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
  }
}

struct Page1: View {
  var body: some View {
    Text("Page1")
  }
}

struct Page2: View {
  var body: some View {
    Text("Page2")
  }
}

struct Page3: View {
  var body: some View {
    Text("Page3")
  }
}

struct PdfView : UIViewRepresentable {
  let pdfDocument: PDFDocument
  
  func makeUIView(context: Context) -> some PDFView {
    let pdfView = PDFView()
    pdfView.document = pdfDocument
    return pdfView
  }
  func updateUIView(_ uiView: UIViewType, context: Context) {}
}

func combinePdf(_ pdfData: Data,_ pdfDataList: Data...) -> PDFDocument? {
  if let basePdfDocument = PDFDocument(data: pdfData){
    pdfDataList.forEach { data in
      let pageNo = basePdfDocument.pageCount
      if let pdfPage = PDFDocument(data: data)?.page(at: 0){
        basePdfDocument.insert(pdfPage, at: pageNo)
      }
    }
    return basePdfDocument
  }
  return nil
}

extension View {
  func toPdfData(width:CGFloat=595.2, height:CGFloat=841.8) -> Data {
    
    let pdfVC = UIHostingController(rootView: self)
    pdfVC.view.frame = CGRect(x: 0, y: 0, width: width, height: height)
    let scenes = UIApplication.shared.connectedScenes
    let windowScene = scenes.first as? UIWindowScene
    let window = windowScene?.windows.first
    let rootVC = window?.rootViewController
    rootVC?.addChild(pdfVC)
    rootVC?.view.insertSubview(pdfVC.view, at: 0)
    let pdfRenderer = UIGraphicsPDFRenderer(bounds: CGRect(x: 0, y: 0, width: width, height: height))
    let pdf = pdfRenderer.pdfData(actions: { context in
      context.beginPage()
      rootVC?.view.layer.render(in: context.cgContext)
    })
    
    pdfVC.removeFromParent()
    pdfVC.view.removeFromSuperview()
    
    return pdf
  }
}