Concurrent Operation in Swift 3

ConcurrentOperation.swift

//
//  ConcurrentOperation.swift
//
//  Created by Caleb Davenport on 7/7/14.
//
//  Learn more at http://blog.calebd.me/swift-concurrent-operations
//

import Foundation

class ConcurrentOperation: Operation {
    
    // MARK: - Types
    
    enum State {
        case ready, executing, finished
        var keyPath: String {
            switch self {
            case .ready:
                return "isReady"
            case .executing:
                return "isExecuting"
            case .finished:
                return "isFinished"
            }
        }
    }
    
    // MARK: - Properties
    
    var state = State.ready {
        willSet {
            willChangeValue(forKey: newValue.keyPath)
            willChangeValue(forKey: state.keyPath)
        }
        didSet {
            didChangeValue(forKey: oldValue.keyPath)
            didChangeValue(forKey: state.keyPath)
        }
    }
    
    // MARK: - NSOperation
    
    override var isReady: Bool {
        return super.isReady && state == .ready
    }
    
    override var isExecuting: Bool {
        return state == .executing
    }
    
    override var isFinished: Bool {
        return state == .finished
    }
    
    override var isAsynchronous: Bool {
        return true
    }
    
}