iOS RxSwift 4.2 how to implement Reactive extension of CBCentralManager using DelegateProxy?

Question

I'm looking at this example of using reactive extensions with Core Bluetooth . However, it is written in swift 3.0 and has a number of errors running in Swift 4.2. I'm interested in implementing a reactive extension of CBCentralManager to provide me with a RX stream of status events.

My understanding is that this allows the proxy to receive delegate events from the CBCentralManager and propagate them to observers using _stateBehaviorSubject: BehaviorSubject<CBManagerState>? However, the project has too many errors and I cannot figure out where do I cut to keep only the functionality I want.

How do I implement the a reactive extension using DelegateProxy for CBCentralManager?

extension Reactive where Base: CBCentralManager {

  public var delegate: DelegateProxy {
    return RxCBCentralManagerDelegateProxy.proxyForObject(base)
  }

  public var state: Observable<CBManagerState> {
    let proxy = RxCBCentralManagerDelegateProxy.proxyForObject(base) //error here
    return proxy.stateBehaviorSubject.skip(1)
  }
}

Answer 1

This is a working implementation for CBCentralManager

extension CBCentralManager : HasDelegate {
    public typealias Delegate = CBCentralManagerDelegate
}

class RxCBCentralManagerDelegateProxy
  : DelegateProxy<CBCentralManager, CBCentralManagerDelegate>
  , DelegateProxyType
  , CBCentralManagerDelegate
{

   internal let stateBehaviorSubject: BehaviorSubject<CBManagerState>

   init(centralManager: CBCentralManager) {
       let subject = BehaviorSubject(value: centralManager.state)
       stateBehaviorSubject = subject

       super.init(parentObject: centralManager, delegateProxy: RxCBCentralManagerDelegateProxy.self)
   }

   func centralManagerDidUpdateState(_ central: CBCentralManager) {
       stateBehaviorSubject.onNext(central.state)
       _forwardToDelegate?.centralManagerDidUpdateState(central)
   }

   static func registerKnownImplementations() {
       self.register { RxCBCentralManagerDelegateProxy(centralManager: $0) }
   }

   deinit {
       stateBehaviorSubject.on(.completed)
   }
}

extension Reactive where Base : CBCentralManager {
   var delegate: DelegateProxy<CBCentralManager, CBCentralManagerDelegate> {
       return RxCBCentralManagerDelegateProxy.proxy(for: base)
   }

   var state: ControlEvent<CBManagerState> {
       let source = (delegate as! RxCBCentralManagerDelegateProxy)
          .stateBehaviorSubject
          .skip(1)
       return ControlEvent(events: source)
   }
}