Angular listen to function that returns some variable

Question

So I have a function in my service that's returning a value and I want my component to be listening to the value and update it when it changes so I thought It would be a good idea to subscribe to it but it doesn't work as intended and doesn't update the value when it changes. Is there a different way to do this?

 ngOnInit(): void {
    this.translateService.onLangChange.subscribe(() => this.getLocaleDateFormat());
  }

 getLocaleDateFormat(): Observable<string> {
   this.dateAdapter.setLocale(Languages[this.translateService.currentLang]);
   this.currLang = Languages[this.translateService.currentLang];
    console.log( 'get' + this.currLang);
    return of (this.currLang);

  }

ngOnInit(): void {
    this.localeDateAdapterService.getLocaleDateFormat().subscribe(currLang => this.currLang = currLang);
}

I don't need to know when it changes I just the value to update when it changes. Without using a timer and also without using OnLangChange as a trigger:

ngOnInit(): void {
 this.translateService.onLangChange.subscribe(() => this.localeDateAdapterService.getLocaleDateFormat().subscribe(currLang => this.currLang = currLang));
}

Answer 1

I made it as as a separate service called LocaleService. You somehow have to get the current language maybe from translate service or if you make it as a separate service that handles it.

private onLanguageChange(lang: string): void {
        // To add another lang:
        // 1. add mapping from EMS language codes to Angular locale codes in the map at the bottom of this file
        // 2. register locale data, also at the bottom of this file
        const locale = Languages[lang];
        this.activeLocale.next(locale);
        this.dateAdapter.setLocale(locale);
        this.LW.log('Language change detected (current lang: ' + lang + '), setting locale to: ' + locale);
      }
    
      public getActiveLocale(): BehaviorSubject<string> {
        return this.activeLocale;
      }
    export const Languages = {
      'eng': 'en',
      'slk': 'sk',
      'cze': 'cs',
    };
    
    registerLocaleData(localeSk);
    registerLocaleData(localeCs);

this goes to the Component

this.localeService.getActiveLocale().subscribe(locale => this.currentLocale = locale));