Angular 角度侦听返回某个变量的函数

因此，我的服务中有一个函数返回一个值，我希望我的组件监听该值，并在它发生变化时更新它，所以我认为订阅它是一个好主意，但它不能按预期工作，并且在它发生变化时不更新该值。有没有其他方法可以做到这一点

 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);
}

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使用/rxjs中的主题

// Service

language$ = new Subject<string>();

setLanguage(lang: string): void {
 this.language$.next(lang);
}


// Component

this.language$.subscribe((res: string) => {
 console.log(res);
});

this.languageSrv.setLanguage('en');
this.languageSrv.setLanguage('es');
this.languageSrv.setLanguage('it');
this.languageSrv.setLanguage('fr');

// 'en'
// 'es'
// 'it'
// 'fr'

//服务
语言$=新主题（）；
setLanguage（lang:string）：无效{
this.language$.next（lang）；
}
//组成部分
this.language$.subscribe（（res:string）=>{
控制台日志（res）；
});
this.languageSrv.setLanguage（'en'）；
this.languageSrv.setLanguage（'es'）；
this.languageSrv.setLanguage（'it'）；
this.languageSrv.setLanguage（'fr'）；
//“嗯”
//“是的”
//“是的。”
//“fr”

---

始终记住取消订阅

我将其作为一项单独的服务，名为LocaleService。您必须以某种方式从translate服务获取当前语言，或者将其作为单独的服务来处理

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);

---

这不会因为组件需要服务而服务需要组件而创建循环依赖关系吗？

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