Checking for states in the NSOperation

MyOperation.swift

import Foundation

class MyOperation:NSOperation{

    // the states of the operation.    
    enum State {
        case Ready, Executing, Finished
        func keyPath() -> String {
            switch self {
            case Ready:
                return "isReady"
            case Executing:
                return "isExecuting"
            case Finished:
                return "isFinished"
            }
        }
    }
    
    // MARK: - Properties
    //this takes care of setting the state property with KVO
    var state = State.Ready {
        willSet {
            willChangeValueForKey(newValue.keyPath())
            willChangeValueForKey(state.keyPath())
        }
        didSet {
            didChangeValueForKey(oldValue.keyPath())
            didChangeValueForKey(state.keyPath())
        }
    }
    
    // you can now easily check for the states as enums
    override var ready: Bool {
        return super.ready && state == .Ready
    }
    
    override var executing: Bool {
        return state == .Executing
    }
    
    override var finished: Bool {
        return state == .Finished
    }
    
    override var asynchronous: Bool {
        return true
    }
}