Download multiple files with progress view

Overview

Download multiple files with progress view. Just drap&drop DownloadManager folder to your xcode project.

Steps

1. Initialize the DownloadManager

Create an instance of DownloadManager and optionally provide handlers for progress updates, task completion, and all task completions. If no handlers are specified, default (empty) handlers will be used.

// Update the progress UI
let progressHandler: ProgressHandler = { progress, downloadLink in
    let progressDescription = String(format: "%0.1f%%", progress * 100)
    print("Progress: \(progressDescription) for file: \(downloadLink?.fileName ?? "Unknown")")
}

// Called when a single download task is complete
let singleCompleteHandler: SingleTaskCompleteHandler = { downloadLink in
    print("Download finished for: \(downloadLink?.fileName ?? "Unknown file")")
}

// Called when all download tasks are complete
let allCompleteHandler: AllTasksCompleteHandler = {
    print("All downloads are completed!")
}

// If download from background this block will be called
// when background downloads are complete 
let backgroundCompletion: () -> Void = {
    if let appDelegate = UIApplication.shared.delegate as? AppDelegate {
        appDelegate.backgroundSessionCompletionHandler?()
    }
    
    print("All tasks completed in background ")
}

// Initialize DownloadManager with external handlers
let downloadManager = DownloadManager(
    progressHandler: progressHandler,
    singleCompleteHandler: singleCompleteHandler,
    allCompleteHandler: allCompleteHandler,
    backgroundCompletion: backgroundCompletion
)

2. Add URLs to the download queue to start download

let downloadLinks = [
    DownloadLink(link: "https://file-examples-com.github.io/uploads/2017/11/file_example_MP3_5MG.mp3"),
    DownloadLink(link: "http://ipv4.download.thinkbroadband.com/50MB.zip"),
    DownloadLink(link: "https://file-examples-com.github.io/uploads/2017/11/file_example_MP3_2MG.mp3"),
    DownloadLink(link: "http://ipv4.download.thinkbroadband.com/20MB.zip"),
    DownloadLink(link: "https://file-examples-com.github.io/uploads/2017/02/zip_10MB.zip")
]

// Add downloads to the manager
downloadManager.addDownload(downloadLinks)

3. Restore pending downloads

When resuming the app or recovering from interruptions (e.g., if the app is force-quit or crashes during downloads), restore any pending downloads using restorePendingDownloads(). This ensures that downloads can continue from where they left off, provided resumeData or any saved state exists.

// Restore any unfinished or pending downloads
downloadManager.restorePendingDownloads()

###　4. Tracking background URLSession To track background downloads session, update your AppDelegate to handle background session events. This ensures that background tasks can notify the app when they are complete.

class AppDelegate: UIResponder, UIApplicationDelegate {
    var backgroundSessionCompletionHandler: (() -> Void)?   
    
    // Add support for background downloads
    func application(_ application: UIApplication, handleEventsForBackgroundURLSession identifier: String, completionHandler: @escaping () -> Void) {
        backgroundSessionCompletionHandler = completionHandler
    }
}

This method is called when a background URLSession completes its tasks. You should store the completionHandler and call it after processing all background events, ensuring the app transitions correctly.

Tip

• When download file from http link, turn ATS on in info.plist

  • App Transport Security Settins -> Allow Arbitrary Loads -> YES

• Change maxOperationCount to make download serially or concurrently .

DownloadManager.maxOperationCount = 1  // download files one by one.

DownloadManager.maxOperationCount = 3  // download files concurrently(max to 3)