title: Angular2 detect change in service
body: <p>I have one component in Angular2 which is changing a "lang" class variable in my service translate.service.ts. In another component I am fetching a dict with the translation on init. If the first component changes the services language later, I want to refetch the dict in the second component automatically. How do I do that?</p>
  
  <p>First component:</p>
  
  <pre><code>  setLang(lang) {
      this._translateService.setLang(lang);
    }
  </code></pre>
  
  <p>Service:</p>
  
  <pre><code>dict = { "en": {}};
  lang = "en";
  
  setLang(lang) {
      this.lang = lang;
  }
  
  getLang() {
      return this.dict;
  }
  </code></pre>
  
  <p>Second component:</p>
  
  <pre><code>ngOnInit() {
      this.dict = this._translateService.getDict();
  }
  </code></pre>