Fix bugs

src/app/services/cancel.service.ts

@@ -0,0 +1,30 @@
+import { Injectable } from '@angular/core';
+
+interface Subscriber {
+  callback: () => void;
+  object: object;
+}
+
+@Injectable({
+  providedIn: 'root'
+})
+export class CancelService {
+  private subscribers: Subscriber[] = [];
+
+  constructor() {}
+
+  subscribe(object: object, callback: () => void) {
+    this.subscribers.push({
+      object,
+      callback
+    });
+  }
+
+  cancelAllExcept(except: object) {
+    this.subscribers.filter(s => s.object !== except).map(s => s.callback());
+  }
+
+  cancelAll() {
+    this.subscribers.map(s => s.callback());
+  }
+}