Reactive extension on UIViewController, adding observables for the basic UIViewController life cycle functions

ReactiveExtensions.swift

import RxSwift
import RxCocoa

extension Reactive where Base: UIViewController {
    
    public var viewDidLoad: Observable<Void> {
        return self.sentMessage(#selector(UIViewController.viewDidLoad)).map({ _ in return () })
    }
    
    public var viewWillAppear: Observable<Bool> {
        return self.sentMessage(#selector(UIViewController.viewWillAppear(_:))).map({ $0.first as! Bool })
    }
    
    public var viewDidAppear: Observable<Bool> {
        return self.sentMessage(#selector(UIViewController.viewDidAppear(_:))).map({ $0.first as! Bool })
    }
    
    public var viewWillDisappear: Observable<Bool> {
        return self.sentMessage(#selector(UIViewController.viewWillDisappear(_:))).map({ $0.first as! Bool })
    }
    
    public var viewDidDisappear: Observable<Bool> {
        return self.sentMessage(#selector(UIViewController.viewDidDisappear(_:))).map({ $0.first as! Bool })
    }
}