Method constructor

src/aria/tree/tree.ts:162–202

()

  readonly activeDescendant: Signal<string | undefined>;

  constructor() {
    const inputs = {
      ...this,
      id: this.id,
      items: computed(() => this._collection.orderedItems().map(item => item._pattern)),
      activeItem: signal<TreeItemPattern<V> | undefined>(undefined),
      element: () => this.element,
    };

    this._pattern = new TreePattern<V>(inputs);

    this.activeDescendant = computed(() => this._pattern.activeDescendant());

    afterNextRender(() => {
      this._collection.startObserving(this.element);
    });

    // Check for any violations after the DOM has been updated.
    if (typeof ngDevMode === 'undefined' || ngDevMode) {
      afterRenderEffect({
        read: () => {
          reportViolations(this._pattern.validate(), this.element);
        },
      });
    }

    // Resets default focus based on selection state until interacted.
    afterRenderEffect({write: () => this._pattern.setDefaultStateEffect()});

    afterRenderEffect({
      write: () => {
        const items = inputs.items();
        const activeItem = untracked(() => inputs.activeItem());

        if (activeItem && !items.some(i => i === activeItem)) {
          this._pattern.treeBehavior.unfocus();
          this._pattern.setDefaultState();
        }
      },
    });
  }

  ngOnDestroy() {
    this._collection.stopObserving();