fix: improve draft manager

Author: khushal87

examples/SampleApp/src/utils/WithSubscription.ts

@@ -0,0 +1,51 @@
+import { Unsubscribe } from 'stream-chat';
+
+/**
+ * @private
+ * Class to use as a template for subscribable entities.
+ */
+export abstract class WithSubscriptions {
+  private unsubscribeFunctions: Set<Unsubscribe> = new Set();
+  /**
+   * Workaround for the missing TS keyword - ensures that inheritants
+   * overriding `unregisterSubscriptions` call the base method and return
+   * its unique symbol value.
+   */
+  private static symbol = Symbol(WithSubscriptions.name);
+
+  public abstract registerSubscriptions(): void;
+
+  /**
+   * Returns a boolean, provides information of whether `registerSubscriptions`
+   * method has already been called for this instance.
+   */
+  public get hasSubscriptions() {
+    return this.unsubscribeFunctions.size > 0;
+  }
+
+  public addUnsubscribeFunction(unsubscribeFunction: Unsubscribe) {
+    this.unsubscribeFunctions.add(unsubscribeFunction);
+  }
+
+  /**
+   * If you re-declare `unregisterSubscriptions` method within your class
+   * make sure to run the original too.
+   *
+   * @example
+   * ```ts
+   * class T extends WithSubscriptions {
+   *  ...
+   *  public unregisterSubscriptions = () => {
+   *    this.customThing();
+   *    return super.unregisterSubscriptions();
+   *  }
+   * }
+   * ```
+   */
+  public unregisterSubscriptions(): typeof WithSubscriptions.symbol {
+    this.unsubscribeFunctions.forEach((unsubscribe) => unsubscribe());
+    this.unsubscribeFunctions.clear();
+
+    return WithSubscriptions.symbol;
+  }
+}