Singleton - notify many subscribers via weak objects set - inspired by article - https://nshipster.com/nshashtable-and-nsmaptable/

SocketClient+Events.swift

extension SocketClient {
    
    enum Event: String, CaseIterable {
        // Chat:
        
        case sendMessage = "speak"
        case typing = "typing"
        case lastSeen = "last_seen"
        case unreadConversations = "unread_conversations"
    }
}

SocketClient+Observation.swift

import Foundation
import SwiftyJSON

protocol SocketActionObserver: class {
  
    func socketDidReceiveState(_ state: SocketClient.ChannelState, for channel: SocketClient.GChannel)
    func socketDidReceiveResponse(for event: SocketClient.Event, data: JSON)
}

extension SocketActionObserver {

    func observeSocket(for events: SocketClient.Event...) {
        observeSocket(for: events)
    }

    func observeSocket(for events: [SocketClient.Event]) {

        for event in events {
            let observers = SocketClient.eventsObservers[event] ?? .init()
            observers.insert(self)
            SocketClient.eventsObservers[event] = observers
        }
    }

    func stopObservingSocket(for events: SocketClient.Event...) {

        for event in events {
            guard let observers = SocketClient.eventsObservers[event] else { continue }
            observers.remove(self)
            SocketClient.eventsObservers[event] = observers
        }
    }

    func stopObservingAllSocketEvents() {

        for event in SocketClient.Event.allCases {
            guard let observers = SocketClient.eventsObservers[event] else { continue }
            observers.remove(self)
            SocketClient.eventsObservers[event] = observers
        }
    }
}

//

extension SocketClient {

    /// Socket event observers.
    fileprivate static var eventsObservers: [SocketClient.Event: WeakSet<SocketActionObserver>] = [:]

    /// Will go through all observers object for given socket event
    /// and will call method related to this action.
    ///
    /// - Parameter event: Event about which observers will be notified.
    /// - Parameter data: JSON data that came along with the event.
    /// - Parameter queue: Operation queue, where the notification will happen.
    func notifyObservers(about event: Event, with data: JSON, queue: OperationQueue = .main) {

        guard let observers = SocketClient.eventsObservers[event]?.allObjects else { return }
        queue.addOperation { observers.forEach { $0.socketDidReceiveResponse(for: event, data: data) } }
    }
    
    func notifyObservers(about state: SocketClient.ChannelState, queue: OperationQueue = .main) {
        
    }
}

SocketClient.swift

// Usage:

import Foundation
import SwiftyJSON

class SocketClient {

   // MARK: - Singleton
    
   static let shared = SocketClient()
    

  enum State: Int, Comparable {

        case unknown = 0 // initial state
        case disconnected // connection is not established
        case rejected // connection is rejected
        case connecting // connecting was started, but not yet finished
        case connected // connection is established, but authentication is not confirmed
        case authenticating // authentication was started, but not yet finished
        case authenticated // connection is established AND authentication is confirmed

        public static func < (left: State, right: State) -> Bool { left.rawValue < right.rawValue }
        public static func <= (left: State, right: State) -> Bool { left.rawValue <= right.rawValue }

        public static func > (left: State, right: State) -> Bool { left.rawValue > right.rawValue }
        public static func >= (left: State, right: State) -> Bool { left.rawValue >= right.rawValue }
    }

  func receiveNewData(_ data: [String: Any]) {
    SocketClient.shared.notifyObservers(about: .sendMessage, with: JSON(data))
  }

}