RxSwift reactive extension for MGLMapViewDelegate methods

MGLMapView+Reactive.swift

import Foundation
import Mapbox
import RxCocoa
import RxSwift

import UIKit


class RxMGLMapViewDelegateProxy: DelegateProxy, MGLMapViewDelegate, DelegateProxyType {
    
    class func currentDelegateFor(object: AnyObject) -> AnyObject? {
        let mapView: MGLMapView = castOrFatalError(object)
        return mapView.delegate
    }
    
    class func setCurrentDelegate(delegate: AnyObject?, toObject object: AnyObject) {
        let mapView: MGLMapView = castOrFatalError(object)
        mapView.delegate = castOptionalOrFatalError(delegate)
    }
    
}


extension MGLMapView {
    
    public var rx_delegate: DelegateProxy {
        return proxyForObject(self) as RxMGLMapViewDelegateProxy
    }
    
    public var rx_mapViewReigionDidChange: Observable<MGLMapView> {
        return rx_delegate.observe("mapView:regionDidChangeAnimated:")
            .map { a in return a[0] as! MGLMapView }
    }
    
    public var rx_mapViewReigionWillChange: Observable<MGLMapView> {
        return rx_delegate.observe("mapView:regionWillChangeAnimated:")
            .map { a in return a[0] as! MGLMapView }
    }
    
    public var rx_mapViewReigionIsChanging: Observable<MGLMapView> {
        return rx_delegate.observe("mapViewRegionIsChanging:")
            .map { a in return a[0] as! MGLMapView }
    }
    
}


// workaround for Swift compiler bug, cheers compiler team :)
func castOptionalOrFatalError<T>(value: AnyObject?) -> T? {
    if value == nil {
        return nil
    }
    let v: T = castOrFatalError(value)
    return v
}

func castOrFatalError<T>(value: AnyObject!, message: String) -> T {
    let maybeResult: T? = value as? T
    guard let result = maybeResult else {
        rxFatalError(message)
        return maybeResult!
    }
    
    return result
}

func castOrFatalError<T>(value: AnyObject!) -> T {
    let maybeResult: T? = value as? T
    guard let result = maybeResult else {
        rxFatalError("Failure converting from \(value) to \(T.self)")
        return maybeResult!
    }
    
    return result
}

func rxFatalErrorAndDontReturn<T>(lastMessage: String) -> T {
    rxFatalError(lastMessage)
    return (nil as T!)!
}

    
func rxFatalError(lastMessage: String) {
        // The temptation to comment this line is great, but please don't, it's for your own good. The choice is yours.
        fatalError(lastMessage)
}