angular 源码 <一> rotuerLinkActive

@Input()
  set routerLinkActive(data: string[]|string) {
    const classes = Array.isArray(data) ? data : data.split(‘ ‘);
    this.classes = classes.filter(c => !!c);
  }

  ngOnChanges(changes: SimpleChanges): void { this.update(); }
  ngOnDestroy(): void { this.subscription.unsubscribe(); }

  private update(): void {
    if (!this.links || !this.linksWithHrefs || !this.router.navigated) return;
    Promise.resolve().then(() => {
      const hasActiveLinks = this.hasActiveLinks();
      if (this.isActive !== hasActiveLinks) {
        (this as any).isActive = hasActiveLinks;
        this.classes.forEach((c) => {
          if (hasActiveLinks) {
            this.renderer.addClass(this.element.nativeElement, c);
          } else {
            this.renderer.removeClass(this.element.nativeElement, c);
          }
        });
      }
    });
  }