Show Multiple Files as a Single PDF using Swift for iOS

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//
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//  Copyright © 2021-2025 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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class MultipleFilesExample: Example {
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    override init() {
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        super.init()
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        title = "Using Multiple Files"
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        contentDescription = "Display a single document backed by multiple PDF data providers."
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        category = .documentDataProvider
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        priority = 40
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate?) -> UIViewController? {
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        let fileNames = ["Placeholder A.pdf", "Placeholder B.pdf", "Placeholder C.pdf", "Placeholder D.pdf"]
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        // Collection of multiple data providers that will be used to display a combined single document.
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        // See https://www.nutrient.io/guides/ios/features/data-providers to learn more about Data Providers.
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        let dataProviders = fileNames.map { fileName -> DataProviding in
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            let fileURL = AssetLoader.assetURL(for: AssetName(rawValue: fileName))
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            // Copy the files to a writable location so that the data providers can write to the backing
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            // file if needed.
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            let writableURL = fileURL.copyToDocumentDirectory()
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            // `FileDataProvider` can be used to read and write to the backing file at the URL.
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            // However that doesn't use file coordination. See use of `CoordinatedFileDataProvider` below.
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            // return FileDataProvider(fileURL: writableURL)
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            // Nutrient also allows you to load PDF from a Data object.
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            // Changes to the PDF document using this data provider will not be written to the disk.
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            // Data mapped to the memory (virtual) can also be used.
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            // let dataContents = try! Data(contentsOf: writableURL, options: .mappedIfSafe)
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            // return DataContainerProvider(data: dataContents)
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            // See AESCryptoDataProviderExample.swift if you wish to use encrypted data provider.
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            // We are using a `CoordinatedFileDataProvider` which is similar to `FileDataProvider`
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            // but also uses file coordination.
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            // See https://www.nutrient.io/guides/ios/features/file-coordination/ for more info on File Coordination.
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            return CoordinatedFileDataProvider(fileURL: writableURL)
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        }
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        // Use the above created data providers to create and load a document.
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        let document = Document(dataProviders: dataProviders)
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        document.title = "Using Multiple Files Example"
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        // Display the document backed by multiple PDF data providers.
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        let controller = PDFViewController(document: document)
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        return controller
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    }
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}