Auto Save PDF Annotation Changes in Swift for iOS

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//
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//  Copyright © 2019-2025 PSPDFKit GmbH. All rights reserved.
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//
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//  The Nutrient sample applications are licensed with a modified BSD license.
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//  Please see License for details. This notice may not be removed from this file.
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//
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import PSPDFKit
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import PSPDFKitUI
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// This class will ask the user as soon as the first annotation has been added/modified where the annotation should be saved, and optionally copies the file to a new location.
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class AnnotationSaveAsForAnnotationEditingExample: Example {
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    override init() {
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        super.init()
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        title = "Save as... for annotation editing"
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        contentDescription = "Adds an alert after detecting annotation writes to define a new save location."
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        category = .annotations
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        priority = 100
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController? {
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        let document = AssetLoader.writableDocument(for: .annualReport, overrideIfExists: false)
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        return SaveAsPDFViewController(document: document)
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    }
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}
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// MARK: PDFViewController
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private class SaveAsPDFViewController: PDFViewController {
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     var hasUserBeenAskedAboutSaveLocation = false
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     private var observer: Any?
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    override func commonInit(with document: Document?, configuration: PDFConfiguration) {
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        super.commonInit(with: document, configuration: configuration)
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        navigationItem.rightBarButtonItems = [thumbnailsButtonItem, annotationButtonItem]
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        let closeButton = UIBarButtonItem(barButtonSystemItem: .close, target: self, action: #selector(closeButtonTapped(_:)))
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        navigationItem.leftBarButtonItems = [closeButton]
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        NotificationCenter.default.addObserver(self, selector: #selector(annotationChangedNotification), name: .PSPDFAnnotationChanged, object: nil)
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        NotificationCenter.default.addObserver(self, selector: #selector(annotationAddedOrRemovedNotification), name: .PSPDFAnnotationsAdded, object: nil)
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        NotificationCenter.default.addObserver(self, selector: #selector(annotationAddedOrRemovedNotification), name: .PSPDFAnnotationsRemoved, object: nil)
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    }
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    deinit {
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    // Clear document cache, so we don't get annotation-artefacts when loading the doc again.
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        SDK.shared.cache.remove(for: document)
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    }
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    // MARK: Private
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    @objc private func closeButtonTapped(_ sender: UIBarButtonItem) {
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        annotationStateManager.state = nil  // Commit any annotations
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        navigationController?.popViewController(animated: true)
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    }
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    @objc private func annotationChangedNotification(_ notification: Notification) {
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        guard let notificationObject = notification.object as? Annotation else { return }
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        processChangeForAnnotation(annotation: notificationObject)
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    }
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    @objc private func annotationAddedOrRemovedNotification(_ notification: NSNotification) {
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        guard let notificationObject = notification.object as? [Annotation] else { return }
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        for annotation in notificationObject {
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            processChangeForAnnotation(annotation: annotation)
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        }
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    }
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    private func processChangeForAnnotation(annotation: Annotation) {
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        if annotation.document == document {
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            self.askUserAboutSaveLocationIfNeeded()
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        }
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    }
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    // Mark - Document Copying Logic
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    // This code assumes that the PDF location itself is writeable, and will fail for documents in the bundle folder.
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    private func askUserAboutSaveLocationIfNeeded() {
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        // Make sure the alert gets displayed only once per session
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        if hasUserBeenAskedAboutSaveLocation {
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            return
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        }
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        hasUserBeenAskedAboutSaveLocation = true
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        let alertController = UIAlertController(title: nil, message: "Would you like to save annotations into the current file, or create a copy to save the annotation changes?", preferredStyle: .alert)
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        alertController.addAction(UIAlertAction(title: "Save to This File", style: .destructive))
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        alertController.addAction(UIAlertAction(title: "Save as Copy", style: .default, handler: { _ in
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            self.replaceDocumentWithCopy()
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        }))
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        present(alertController, animated: true, completion: nil)
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    }
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    private func replaceDocumentWithCopy() {
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        guard let documentURL = document?.fileURL else { return }
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        let newURL = adjustedFileURLForDocumentURL(documentURL)
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        do {
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            try FileManager.default.copyItem(at: documentURL, to: newURL)
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            // Since the annotation has already been edited, we copy the file *before* it will be saved
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            // then save the current state and switch out the documents.
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        } catch {
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            print("Failed to copy file to \(newURL.path): \(error.localizedDescription)")
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            return
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        }
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        do {
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            try document?.save()
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        } catch {
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            print("Failed to save document: \(error.localizedDescription)")
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        }
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        let tmpURL = newURL.appendingPathExtension("temp")
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        do {
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            try FileManager.default.moveItem(at: documentURL, to: tmpURL)
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        } catch {
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            print("Failed to move file: \(error.localizedDescription)")
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            return
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        }
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        do {
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            try FileManager.default.moveItem(at: newURL, to: documentURL)
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        } catch {
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            print("Failed to move file: \(error.localizedDescription)")
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            return
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        }
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        do {
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            try FileManager.default.moveItem(at: tmpURL, to: newURL)
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        } catch {
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            print("Failed to move file: \(error.localizedDescription)")
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            return
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        }
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        // Finally update the fileURL, this will clear the current document cache.
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        let newDocument = Document(url: newURL)
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        newDocument.title = document?.title // Preserve the title
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        // Preserve annotation selection
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        guard var pageView: PDFPageView = pageViewForPage(at: pageIndex) else { return }
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        guard let selectedAnnotations = pageView.selectedAnnotations else { return }
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        document = newDocument
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        // Restore selection
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        pageView = pageViewForPage(at: pageIndex)!
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        var newSelectedAnnotations: [Annotation] = []
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        for annotation in newDocument.annotationsForPage(at: pageIndex, type: .all) {
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            for selectedAnnotation in selectedAnnotations where annotation.name == selectedAnnotation.name {
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                newSelectedAnnotations.append(annotation)
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            }
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        }
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        // To re-show the popover, we need to wait until the alert view disappears.
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        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.3, execute: {
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            pageView.select(annotations: newSelectedAnnotations, presentMenu: true, animated: true)
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        })
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    }
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    /// Appends `_annotated` to the file basename. Also appends an incrementing integer if a file with a matching name already exists.
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    ///
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    /// For example, `Document.pdf` would change to `Document_annotated.pdf`.
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    /// If `Document_annotated.pdf` already exists then `Document_annotated1.pdf` would be generated instead. Then `Document_annotated2.pdf` etc.
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    private func adjustedFileURLForDocumentURL(_ documentURL: URL) -> URL {
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        var appendFileCount = 0
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        var newPath: NSString
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        repeat {
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            newPath = documentURL.path as NSString
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            let appendSuffix = "_annotated\(appendFileCount == 0 ? "" : "\(appendFileCount)").pdf"
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            if newPath.lowercased.hasSuffix(".pdf") {
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                newPath = newPath.replacingOccurrences(of: ".pdf", with: appendSuffix, options: .caseInsensitive, range: NSRange(location: newPath.length - 4, length: 4)) as NSString
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            } else {
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                newPath = newPath.appending(appendSuffix) as NSString
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            }
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            appendFileCount += 1
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        } while FileManager.default.fileExists(atPath: newPath as String)
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        return NSURL.fileURL(withPath: newPath as String)
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    }
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}