Download PDF from URL using Swift for iOS

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//
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//  Copyright © 2020-2025 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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/// The downloaded document will be read-only.
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/// If you want the document to be writable or want more fine-grained control, see `DocumentProgressExample` instead.
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class RemoteDocumentURLExample: Example {
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    override init() {
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        super.init()
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        title = "Download and show a PDF from a remote URL"
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        contentDescription = "Automatically downloads a PDF with a progress indicator. Optionally caches it for offline storage."
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        category = .documentDataProvider
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        targetDevice = [.vision, .phone, .pad]
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        priority = 1
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    }
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    let url = URL(string: "https://github.com/PSPDFKit/pspdfkit-ios-catalog/raw/master/Samples/Magazine.pdf")!
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    let alwaysDownloadFile = true
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        clearCacheIfNecessary()
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        let document = Document(url: url)
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        let controller = PDFViewController(document: document)
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        return controller
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    }
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    private func clearCacheIfNecessary() {
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        guard alwaysDownloadFile else { return }
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        // Downloads by default use this custom, large cache to ensure files are being updated correctly.
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        // Set the cache to nil to disable this caching.
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        // https://www.nutrient.io/blog/downloading-large-files-with-urlsession/
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        URLDataProvider.cache = nil
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        // Ensure the temporary file does not exist.
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        try? FileManager.default.removeItem(at: URLDataProvider.defaultTargetURL(for: url)!)
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    }
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}