Cache expiration for meta.last_update on an object's own channel.

Proper/Connection/CachedConnection.swift

@@ -34,7 +34,8 @@ class CachedConnection<C: ConnectionType>: ConnectionType {
  // terminates.
  func subscribe(to topic: String) -> EventProducer {
  return connection.subscribe(to: topic)
- .on(value: { [weak self] in _ = self?.cache.store(event: $0, topic: topic) })
+ .on(terminated: { [weak self] in self?.cache.expire(lastEventFrom: topic, on: topic) },
+ value: { [weak self] in _ = self?.cache.store(event: $0, topic: topic) })
  }
 }
 

Proper/Connection/LastEventCache.swift

@@ -10,7 +10,8 @@ import Foundation
 
 /// `NSCache`-backed storage for looking up responses to `meta.last_event`.
 class LastEventCache: NSObject {
- let cache = NSCache<NSString, Box<TopicEvent>>()
+ private let cache = NSCache<NSString, Box<TopicEvent>>()
+ private var voids = [String: DispatchWorkItem]()
 
  /// Create a cache which retains around `numEvents` events (default 100).
  init (numEvents: Int = 100) {
@@ -42,16 +43,29 @@ class LastEventCache: NSObject {
  /// Store `event` in the cache. `event` must have an originator. Returns `true` if stored.
  func store(event: TopicEvent, topic: String) {
  if let originator = event.originator {
- cache.setObject(Box(event), forKey: key(topic, originator) as NSString)
+ let key = self.key(topic, originator)
+ voids[key]?.cancel()
+ cache.setObject(Box(event), forKey: key as NSString)
  }
  }
 
  /// Request `topic` to be removed from the cache at the end of the main loop.
- @available(*, deprecated: 1.0, message: "Functionality removed, is now a no-op")
+ @available(*, unavailable, message: "Use expire(lastEventFrom:on)")
  func void(topic: String) {
  return
  }
 
+ /// Informs the cache that a particular `lastEvent` will no longer be updated and will no longer be guaranteed valid. 
+ func expire(lastEventFrom originator: String, on topic: String) {
+ let key = self.key(topic, originator)
+ let action = DispatchWorkItem { [weak self] in
+ self?.cache.removeObject(forKey: key as NSString)
+ self?.voids[key] = nil
+ }
+ voids[key] = action
+ DispatchQueue.main.async(execute: action)
+ }
+
  private static func eventParams(_ proc: String, _ args: WampArgs) -> (metaTopic: String, originator: String)? {
  guard let metaTopic = args[safe: 0] as? String, let originator = args[safe: 1] as? String,
  proc == "meta.last_event" else {