Live query update (#81)

* Adds support for update operator

* Fix updating currentQuery insubscription

* Makes sure we copy the subscriptions

Author: flovilmart

Sources/ParseLiveQuery/Client.swift

@@ -164,6 +164,26 @@ extension Client {
         return handler
     }
 
+    /**
+     Updates an existing subscription with a new query.
+     Upon completing the registration, the subscribe handler will be called with the new query
+
+     - parameter handler: The specific handler to update.
+     - parameter query:   The new query for that handler.
+     */
+    public func update<T>(
+        _ handler: T,
+        toQuery query: PFQuery<T.PFObjectSubclass>
+        ) where T: SubscriptionHandling {
+        subscriptions = subscriptions.map {
+            if $0.subscriptionHandler === handler {
+                _ = sendOperationAsync(.update(requestId: $0.requestId, query: query as! PFQuery<PFObject>))
+                return SubscriptionRecord(query: query, requestId: $0.requestId, handler: $0.subscriptionHandler as! T)
+            }
+            return $0
+        }
+    }
+
     /**
      Unsubscribes all current subscriptions for a given query.
 
@@ -187,11 +207,10 @@ extension Client {
     func unsubscribe(matching matcher: @escaping (SubscriptionRecord) -> Bool) {
         subscriptions.filter {
             matcher($0)
-            }.forEach {
-                _ = sendOperationAsync(.unsubscribe(requestId: $0.requestId))
+        }.forEach {
+            _ = sendOperationAsync(.unsubscribe(requestId: $0.requestId))
         }
     }
-    
 }
 
 extension Client {

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>, sessionToken: String?)
+    case update(requestId: Client.RequestId, query: PFQuery<PFObject>)
     case unsubscribe(requestId: Client.RequestId)
 
     var JSONObjectRepresentation: [String : Any] {
@@ -27,6 +28,9 @@ enum ClientOperation {
             }
             return result
 
+        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 ]
         }