Adds support for update operator

Sources/ParseLiveQuery/Client.swift

@@ -163,6 +163,31 @@ extension Client {
         return handler
     }
 
+    public func update<T>(
+        _ fromQuery: PFQuery<T>,
+        toQuery query: PFQuery<T>,
+        subclassType: T.Type = T.self
+        ) where T: PFObject  {
+        update(toQuery: query) { $0.query == fromQuery }
+    }
+
+    public func update<T>(
+        _ subscription: Subscription<T>,
+        toQuery query: PFQuery<T>) where T: PFObject {
+        update(toQuery: query) {
+            $0.subscriptionHandler === subscription
+        }
+    }
+
+    func update<T>(
+        toQuery query: PFQuery<T>,
+        matching matcher: @escaping (SubscriptionRecord) -> Bool
+        ) where T: PFObject {
+        subscriptions(matching: matcher).forEach {
+            _ = sendOperationAsync(.update(requestId: $0.requestId, query: query as! PFQuery<PFObject>))
+        }
+    }
+
     /**
      Unsubscribes all current subscriptions for a given query.
 
@@ -184,12 +209,16 @@ extension Client {
     }
 
     func unsubscribe(matching matcher: @escaping (SubscriptionRecord) -> Bool) {
-        subscriptions.filter {
-            matcher($0)
-            }.forEach {
+        subscriptions(matching: matcher).forEach {
                 _ = sendOperationAsync(.unsubscribe(requestId: $0.requestId))
         }
     }
+
+    func subscriptions(matching matcher: @escaping (SubscriptionRecord) -> Bool)  -> [SubscriptionRecord] {
+        return subscriptions.filter {
+            matcher($0)
+        }
+    }
 
 }
 

Sources/ParseLiveQuery/Internal/Operation.swift

@@ -13,6 +13,7 @@ import Parse
 enum ClientOperation {
     case connect(applicationId: String, sessionToken: String)
     case subscribe(requestId: Client.RequestId, query: PFQuery<PFObject>)
+    case update(requestId: Client.RequestId, query: PFQuery<PFObject>)
     case unsubscribe(requestId: Client.RequestId)
 
     var JSONObjectRepresentation: [String : Any] {
@@ -23,6 +24,9 @@ enum ClientOperation {
         case .subscribe(let requestId, let query):
             return [ "op": "subscribe", "requestId": requestId.value, "query": Dictionary<String, AnyObject>(query: query) ]
 
+        case .update(let requestId, let query):
+            return [ "op": "update", "requestId": requestId.value, "query": Dictionary<String, AnyObject>(query: query) ]
+
         case .unsubscribe(let requestId):
             return [ "op": "unsubscribe", "requestId": requestId.value ]
         }