PostProcessing.md

How Post-process works

Overview

DMSwift may have several post-processes.
Post-processing can only be assigned during the initialization of DMSwift. During initialization, DMSwift initializes the PostProcessQueue with a list of post-processes.
With each successfully downloaded file, PostProcessQueue starts post-processing one by one.
During post-processing, the downloaded file is checked for the file extension, if post-processing can process this file, post-processing will then start. Over one file, several post-processing operations can be carried out in turn.

How To Create PostProcessing

To create you need to go through 4 basic steps:

1. Create your struct object that will be inherited from the PostProcessing protocol
2. Specify supported file resolution
3. Implement actions while receiving data for post-processing in the prepare method
4. Implement the post-processing process in the process method
5. Call onComplete after post-process is complete.

Example

Let's say you want to create post-processing for unzipping a file:

public struct ZipProcessing: PostProcessing {

}

First you need to specify which file extension your post-processing will process:

public struct ZipProcessing: PostProcessing {
	public var supportedFileExtensions: Set<String> = ["zip"]
}

Implement actions while receiving data for post-processing in the prepare method:

public struct ZipProcessing: PostProcessing {
    private var sourceLocation: URL?
    private var fileManager: FileStorageManager?

    public mutating func prepare(fileManager: FileStorageManager?, filename: String?, fileExtention: String?, sourceLocation: URL?) {
        self.fileManager = fileManager
        self.sourceLocation = sourceLocation
    }
}

Implement the post-processing process in the process method:

public struct ZipProcessing: PostProcessing {
    private var sourceLocation: URL?
    private var fileManager: FileStorageManager?

    public func process() {
        guard let fileManager = fileManager else { return }
        guard let sourceLocation = sourceLocation else { return }
        guard let directoryUrl = fileManager.directoryURL else { return }
			// process logic
			…
			try? fileManager.fileManager.unzipItem(at: sourceLocation, to: directoryUrl, progress: progress)
    }
}

Call onComplete after post-process is complete:

public struct ZipProcessing: PostProcessing {
    private var sourceLocation: URL?
    private var fileManager: FileStorageManager?

    public func process() {
			var error: Error? = nil
			// process logic
			…
			onComplete?(error)
    }
}