Issue 6916 - Encapsulate filter subscriptions

lib/filterClasses.js

Index: lib/filterClasses.js
===================================================================
--- a/lib/filterClasses.js
+++ b/lib/filterClasses.js
@@ -35,44 +35,82 @@
  * Abstract base class for filters
  *
  * @param {string} text   string representation of the filter
  * @constructor
  */
 function Filter(text)
 {
   this.text = text;
-  this.subscriptions = new Set();
+
+  /**
+   * Subscriptions to which this filter belongs.
+   * @type {Set.<Subscription>}
+   * @private
+   */
+  this._subscriptions = new Set();
 }
 exports.Filter = Filter;
 
 Filter.prototype =
 {
   /**
    * String representation of the filter
    * @type {string}
    */
   text: null,
 
   /**
-   * Filter subscriptions the filter belongs to
-   * @type {Set.<Subscription>}
-   */
-  subscriptions: null,
-
-  /**
    * Filter type as a string, e.g. "blocking".
    * @type {string}
    */
   get type()
   {
     throw new Error("Please define filter type in the subclass");
   },
 
   /**
+   * Yields subscriptions to which the filter belongs.
+   * @yields {Subscription}
+   */
+  *subscriptions()
+  {
+    yield* this._subscriptions;
+  },
+
+  /**
+   * The number of subscriptions to which the filter belongs.
+   * @type {number}
+   */
+  get subscriptionCount()
+  {
+    return this._subscriptions.size;
+  },
+
+  /**
+   * Adds a subscription to the set of subscriptions to which the filter
+   * belongs.
+   * @param {Subscription} subscription
+   */
+  addSubscription(subscription)
+  {
+    this._subscriptions.add(subscription);
+  },
+
+  /**
+   * Removes a subscription from the set of subscriptions to which the filter
+   * belongs.
+   * @param {Subscription} subscription
+   */
+  removeSubscription(subscription)
+  {
+    this._subscriptions.delete(subscription);
+  },
+
+  /**
    * Serializes the filter to an array of strings for writing out on the disk.
    * @param {string[]} buffer  buffer to push the serialization results into
    */
   serialize(buffer)
   {
     buffer.push("[Filter]");
     buffer.push("text=" + this.text);
   },