SDDownloadManager

A simple and robust download manager for iOS (Swift 5) based on URLSession to deal with asynchronous downloading and management of multiple files.

SDDownloadManager is a singleton instance and can thus be called in your code safely from wherever you need to. The idea of writing yet another download manager library stemmed from the fact there are no available open source projects written using Swift based on the new URLSession APIs.

Background downloads are supported starting from version 1.1.0

SDDownloadManager leverages the power of URLSession and URLSessionDownloadTask to make downloading of files and keeping track of their progress a breeze. Originally inspired by TWRDownloadManager (https://github.com/chasseurmic/TWRDownloadManager)

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Minimum iOS version support

iOS 12.0

Installing the library

To use the library, just add the dependency to your Podfile:

platform :ios
pod 'SDDownloadManager', '2.0.0'

Run pod install to install the dependencies.

Usage

SDDownloadManager provides APIs for the following tasks:

• Downloading multiple files asynchronusly to your specified directory.
• Keeping track of download progress and download completion via closure syntax, no need to implement delegates!

Downloading files

public func dowloadFile(withRequest request: URLRequest,
                        inDirectory directory: String? = nil,
                        withName fileName: String? = nil,
                        onProgress progressBlock:DownloadProgressBlock? = nil,
                        onCompletion completionBlock:@escaping DownloadCompletionBlock) -> String? 

Parameters :

• request : A URLRequest which represents a downloadable resource.

• directory : A String which represents a directory name inside the Caches directory of the app.

All the files, once downloaded will be moved from the /tmp directory of the device to the Caches directory. This is done for two reasons:

1. The /tmp directory can be cleaned once in a while to make sure that any partial, cancelled or failed downloads get properly disposed of and do not occupy space both on the device and in iTunes backups.
2. The Caches directory is not synced by default with the user's iCloud documents. This is in compliance with Apple's rules about content that – not being user-specific – can be re-downloaded from the internet and should not be synced with iCloud.

If a directory name is provided, a new sub-directory will be created in the Cached directory.

• fileName : Once the file is finished downloading, if a fileName was provided by the user, it will be used to store the file in its final destination. If no name was provided the manager will use by default the suggested file name that comes in the response parameter OR last path component of the URL string (e.g. for http://www.example.com/files/my_image.jpg, the final file name would be my_image.jpg).

• progressBlock : Called back with a CGFloat value ranging from 0 to 1.0 when the download progresses.

• completionBlock : Called back with two parameters error and fileUrl.

  • If the download was successful, fileUrl represents the URL of the file. The file can be accessed using this url.
  • If the download was unsuccessful, error represents the error that occured in the downloading process.

Calling this method

SDDownloadManager.shared.downloadFile( /*Params */)

return

• The method returns a key which is unique to that download call. Ideally, this key can be used later for cancelling the download or altering the progress block of a specific download. If a download with the speicied urlrequest already exists, this method returns nil.

Downloading files in background

The parameter shouldDownloadInBackground to the method downloadFile() decides whether the download should occur using a background session. For background downloads to be supported, add this to your AppDelegate

func application(_ application: UIApplication, handleEventsForBackgroundURLSession identifier: String, completionHandler: @escaping () -> Void) {
    debugPrint("handleEventsForBackgroundURLSession: \(identifier)")
    SDDownloadManager.shared.backgroundCompletionHandler = completionHandler
}

If you want to show a local notification after all background downloads finish, set showLocalNotificationOnBackgroundDownloadDone to true. You can set the text of local notification using localNotificationText property, Refer the following snippet :

SDDownloadManager.shared.showLocalNotificationOnBackgroundDownloadDone = true  // Set this if you want to issue a local notification when all the background downloads complete.
SDDownloadManager.shared.localNotificationText = "All background downloads complete"  // Text for the local notification
let downloadKey = SDDownloadManager.shared.downloadFile(withRequest: request, inDirectory: directoryName, withName: directoryName, shouldDownloadInBackground: true, onProgress: { (progress) in
        let percentage = String(format: "%.1f %", (progress * 100))
        debugPrint("Background progress : \(percentage)")
    }) { [weak self] (error, url) in
        if let error = error {
            print("Error is \(error as NSError)")
        } else {
            if let url = url {
                print("Downloaded file's url is \(url.path)")
            }
        }
    }

Checking for current downloads

To check if a file is being downloaded, you can use one of the following methods:

public func isDownloadInProgress(forKey key:String?) -> Bool

To get all the dowloads that are in progress:

public func currentDownloads() -> [String]

To alter the blocks of an ongoing download:

public func alterDownload(withKey key:String?,
                          onProgress progressBlock:DownloadProgressBlock?,
                          onCompletion completionBlock:@escaping DownloadCompletionBlock)

Cancelling downloads

To cancel all downloads:

public func cancelAllDownloads()

To cancel a specific download:

public func cancelDownload(forUniqueKey key:String?)

Requirements

SDDownloadManager requires iOS 12.x or greater.

Future Enhancements

I'm planning to integrate the following features in upcoming releases :

• Background Downloads. (Now supported starting from version 1.1.0)
• Resumable Downloads.
• A better and clean example project with more demonstration. (It will be great if I get some help in this from those who are actually using it!)

License

Usage is provided under the MIT License. See LICENSE for the full details.

Contributions

All contributions are welcome. Please fork the project to add functionalities and submit a pull request to merge them in next releases.