A sample of creating custom delegate for RxSwift [Reference: http://blog.edenmsg.com/rxswift-migrate-delegates-to-beautiful-observables/]

RxTTTAttributedLabel.swift

import TTTAttributedLabel
import RxSwift
import RxCocoa

fileprivate class RxTTTAttributedLabelDelegateProxy: DelegateProxy, TTTAttributedLabelDelegate, DelegateProxyType {
  //We need a way to read the current delegate
  static func currentDelegateFor(_ object: AnyObject) -> AnyObject? {
    let label: TTTAttributedLabel = object as! TTTAttributedLabel
    return label.delegate
  }
  //We need a way to set the current delegate
  static func setCurrentDelegate(_ delegate: AnyObject?, toObject object: AnyObject) {
    let label: TTTAttributedLabel = object as! TTTAttributedLabel
    label.delegate = delegate as? TTTAttributedLabelDelegate
  }
}

extension Reactive where Base : TTTAttributedLabel {

  var delegate: DelegateProxy  {
    return RxTTTAttributedLabelDelegateProxy.proxyForObject(base)
  }
  
  var linkDidTap: Observable<URL> {
    let selector = #selector(
      ((TTTAttributedLabelDelegate.attributedLabel(_:didSelectLinkWith:))!
        as (TTTAttributedLabelDelegate) -> (TTTAttributedLabel, URL) -> Void))
    return delegate.observe(selector)
      .map { params in
        return params[1] as! URL
    }
  }
}

When you face a problem of ambiguous use of a selector, you should read this article https://www.bignerdranch.com/blog/hannibal-selector/.

Swift selector is a bit tricky :-)