improved the type safety by introducing a template parameter extending a type union of all possible return types.

Author: janniclas

client/src/app/api/api/socket.service.ts

@@ -32,9 +32,9 @@ import {InstanceLink} from '../model/instanceLink';
 
 
 interface ObserverMap {
-  [key: string]: Subject<any>;
+  [key: string]: Subject<ReturnType>;
 }
-
+type ReturnType = Instance | InstanceLink | number | DockerOperationError;
 @Injectable({
   providedIn: 'root'
 })
@@ -89,9 +89,8 @@ export class SocketService {
    *
    * @param eventName
    */
-  public subscribeForEvent(eventName: EventType): Observable<number | InstanceLink | Instance | DockerOperationError> {
-
-    return new Observable((observer: Observer<any>) => {
+  public subscribeForEvent<T extends ReturnType>(eventName: EventType): Observable<T> {
+    return new Observable<T>((observer: Observer<T>) => {
 
       /**
        * First step to subscribe for an event is to append the new observer to the set
@@ -111,7 +110,7 @@ export class SocketService {
       }
 
       if (!registeredEvents.includes(eventName)) {
-        this.observers[eventName] = new Subject<any>();
+        this.observers[eventName] = new Subject<T>();
         console.log('registering for event', eventName);
 
         this.send({event: publishEventName});
@@ -144,7 +143,7 @@ export class SocketService {
 
         const {event, toSend} = this.getEventAndPayload(msg);
 
-        const relevantSubject: Subject<any> = this.observers[event];
+        const relevantSubject = this.observers[event];
         if (relevantSubject) {
           relevantSubject.next(toSend);
         }
@@ -165,7 +164,7 @@ export class SocketService {
    * @param msg
    */
   private getEventAndPayload(msg: RegistryEvent) {
-    let toSend: any;
+    let toSend: ReturnType;
     let event: EventType;
 
     if (msg.eventType === EventTypeEnum.NumbersChangedEvent) {

client/src/app/dashboard/dashboard-card/dashboard-card.component.ts

@@ -69,7 +69,7 @@ export class DashboardCardComponent implements OnInit {
 
       const eventType: EventType = DashboardCardComponent.compTypeEventMap[this.componentType];
 
-      this.socketService.subscribeForEvent(eventType).subscribe((data: number) => {
+      this.socketService.subscribeForEvent<number>(eventType).subscribe((data: number) => {
         console.log('data callback in card component', data);
 
         this.numberOfInstances = '' + data;