Creating an RxSwift Observable from a closure

ClosureAsRxObservable.swift

// Say we have an Alamofire request we want to consume as an Observable..

func fooAsObservable(URL: String, headers: [String: AnyObject?]) -> Observable<Foo> {

    return create { observer in

      let request = Alamofire(.GET, URL, headers: headers
           .responseJSON(completionHandler: { (_, _, result) in
               switch result {
                  case .Failure(let data, let error):
                      observer.on(.Error(error)
                  case .Success(let value):
                      let foo = Foo(value)
                      observer.on(.Next(foo))
                      observer.on(.Completed)
               }
           
           })
           
        return AnonymousDisposable {
            request.cancel()
        }
           
    }
}