RxRealm pod 更新后在 RxRealm.swift 中构建编译错误：类型“List”不符合协议“NotificationEmitter”

这是文件 RxRealm.swift 的顶部部分。 （文件中的其他地方都没有编译错误，也没有“观察”函数。

//
//  RxRealm extensions
//
//  Copyright (c) 2016 RxSwiftCommunity. All rights reserved.
//  Check the LICENSE file for details
//  Created by Marin Todorov
//

import Foundation
import RealmSwift
import RxSwift

public enum RxRealmError: Error {
  case objectDeleted
  case unknown
}

// MARK: Realm Collections type extensions

/**
 `NotificationEmitter` is a protocol to allow for Realm's collections to be handled in a generic way.

 All collections already include a `addNotificationBlock(_:)` method - making them conform to `NotificationEmitter` just makes it easier to add Rx methods to them.

 The methods of essence in this protocol are `asObservable(...)`, which allow for observing for changes on Realm's collections.
 */
public protocol NotificationEmitter {
  associatedtype ElementType: RealmCollectionValue

  /**
   Returns a `NotificationToken`, which while retained enables change notifications for the current collection.

   - returns: `NotificationToken` - retain this value to keep notifications being emitted for the current collection.
   */
  func observe(on queue: DispatchQueue?, _ block: @escaping (RealmCollectionChange<Self>) -> Void) -> NotificationToken

  func toArray() -> [ElementType]

  func toAnyCollection() -> AnyRealmCollection<ElementType>
}

extension List: NotificationEmitter {
  public func toAnyCollection() -> AnyRealmCollection<Element> {
    return AnyRealmCollection<Element>(self)
  }

  public typealias ElementType = Element
  public func toArray() -> [Element] {
    return Array(self)
  }
}

extension AnyRealmCollection: NotificationEmitter {
  public func toAnyCollection() -> AnyRealmCollection<Element> {
    return AnyRealmCollection<ElementType>(self)
  }

  public typealias ElementType = Element
  public func toArray() -> [Element] {
    return Array(self)
  }
}

extension Results: NotificationEmitter {
  public func toAnyCollection() -> AnyRealmCollection<Element> {
    return AnyRealmCollection<ElementType>(self)
  }

  public typealias ElementType = Element
  public func toArray() -> [Element] {
    return Array(self)
  }
}

extension LinkingObjects: NotificationEmitter {
  public func toAnyCollection() -> AnyRealmCollection<Element> {
    return AnyRealmCollection<ElementType>(self)
  }

  public typealias ElementType = Element
  public func toArray() -> [Element] {
    return Array(self)
  }
}

我尝试按照建议添加协议存根，但我不知道添加的观察函数内部有什么内容。

public func observe(on queue: DispatchQueue?, _ block: @escaping (RealmCollectionChange<List<Element>>) -> Void) -> NotificationToken {
        // what goes here? 
    }

我尝试将函数留空，但它会抛出另一个错误：“预期返回‘NotificationToken’（又名‘RLMNotificationToken’）的函数中缺少返回”

如果我放入一个返回函数，我不知道该放什么。显然它是 NotificiationToken 类型，但现在我迷路了。

这确实超出了我的想象，但 Cocoapods 上没有任何相关内容https://cocoapods.org/pods/RxRealm https://cocoapods.org/pods/RxRealm

任何想法如何解决这一问题？

为我工作：

pod 'Realm', '10.20.1'  
pod 'RealmSwift', '10.20.1'  
pod 'RxRealm', '4.0.3'