/**
  * A constructor that injects many services.
  * 
  * @param authService Authorization service. 
  * @param translateService Translating service.
  * @param changeDetectorRef Change detector references.
  * @param media A media matcher.
  */
 constructor(
   private authService: AuthService, 
   private translateService: TranslateService, 
   changeDetectorRef: ChangeDetectorRef, 
   media: MediaMatcher
 ) { 
   this.mobileQuery = media.matchMedia('(max-width: 600px)');
   this._mobileQueryListener = () => changeDetectorRef.detectChanges();
   this.mobileQuery.addListener(this._mobileQueryListener);
 }

 constructor(changeDetectorRef: ChangeDetectorRef, media: MediaMatcher, public menuItems: MenuItems) {
   
   this.mobileQuery = media.matchMedia('(min-width: 768px)');
   this._mobileQueryListener = () => changeDetectorRef.detectChanges();
   this.mobileQuery.addListener(this._mobileQueryListener);
 }

 constructor(changeDetectorRef: ChangeDetectorRef, media: MediaMatcher) {
   this.mobileQuery = media.matchMedia('(max-width: 600px)');
   this._mobileQueryListener = () => changeDetectorRef.detectChanges();
   this.mobileQuery.addListener(this._mobileQueryListener);
 }