Created
February 25, 2018 14:41
-
-
Save hurshagrawal/9907878f4e342a738a1c9ea002660f5b to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| // Copyright © 2017 Jumprope. All rights reserved. | |
| import Foundation | |
| // From: https://stackoverflow.com/questions/32322386/how-to-download-multiple-files-sequentially-using-nsurlsession-downloadtask-in-s | |
| // Asynchronous operation base class | |
| // | |
| // This is abstract to class performs all of the necessary KVN of `isFinished` and | |
| // `isExecuting` for a concurrent `Operation` subclass. You can subclass this and | |
| // implement asynchronous operations. All you must do is: | |
| // | |
| // - override `main()` with the tasks that initiate the asynchronous task; | |
| // | |
| // - call `completeOperation()` function when the asynchronous task is done; | |
| // | |
| // - optionally, periodically check `self.cancelled` status, performing any clean-up | |
| // necessary and then ensuring that `completeOperation()` is called; or | |
| // override `cancel` method, calling `super.cancel()` and then cleaning-up | |
| // and ensuring `completeOperation()` is called. | |
| public class AsynchronousOperation: Operation { | |
| override public var isAsynchronous: Bool { return true } | |
| private let stateLock = NSLock() | |
| private var _executing: Bool = false | |
| override private(set) public var isExecuting: Bool { | |
| get { | |
| return stateLock.withCriticalScope { _executing } | |
| } | |
| set { | |
| willChangeValue(forKey: "isExecuting") | |
| stateLock.withCriticalScope { _executing = newValue } | |
| didChangeValue(forKey: "isExecuting") | |
| } | |
| } | |
| private var _finished: Bool = false | |
| override private(set) public var isFinished: Bool { | |
| get { | |
| return stateLock.withCriticalScope { _finished } | |
| } | |
| set { | |
| willChangeValue(forKey: "isFinished") | |
| stateLock.withCriticalScope { _finished = newValue } | |
| didChangeValue(forKey: "isFinished") | |
| } | |
| } | |
| // Complete the operation | |
| // | |
| // This will result in the appropriate KVN of isFinished and isExecuting | |
| public func completeOperation() { | |
| if isExecuting { | |
| isExecuting = false | |
| } | |
| if !isFinished { | |
| isFinished = true | |
| } | |
| } | |
| override public func start() { | |
| if isCancelled { | |
| isFinished = true | |
| return | |
| } | |
| isExecuting = true | |
| main() | |
| } | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment