Method renderNodeChanges

src/cdk/tree/tree.ts:513–568

Check for changes made in the data and render each change (node added/removed/moved).

(
    data: readonly T[],
    dataDiffer: IterableDiffer<T> = this._dataDiffer,
    viewContainer: ViewContainerRef = this._nodeOutlet.viewContainer,
    parentData?: T,
  )

  /** Check for changes made in the data and render each change (node added/removed/moved). */
  renderNodeChanges(
    data: readonly T[],
    dataDiffer: IterableDiffer<T> = this._dataDiffer,
    viewContainer: ViewContainerRef = this._nodeOutlet.viewContainer,
    parentData?: T,
  ) {
    const changes = dataDiffer.diff(data);

    // Some tree consumers expect change detection to propagate to nodes
    // even when the array itself hasn't changed; we explicitly detect changes
    // anyways in order for nodes to update their data.
    //
    // However, if change detection is called while the component's view is
    // still initing, then the order of child views initing will be incorrect;
    // to prevent this, we only exit early if the view hasn't initialized yet.
    if (!changes && !this._viewInit) {
      return;
    }

    changes?.forEachOperation(
      (
        item: IterableChangeRecord<T>,
        adjustedPreviousIndex: number | null,
        currentIndex: number | null,
      ) => {
        if (item.previousIndex == null) {
          this.insertNode(data[currentIndex!], currentIndex!, viewContainer, parentData);
        } else if (currentIndex == null) {
          viewContainer.remove(adjustedPreviousIndex!);
        } else {
          const view = viewContainer.get(adjustedPreviousIndex!);
          viewContainer.move(view!, currentIndex);
        }
      },
    );

    // If the data itself changes, but keeps the same trackBy, we need to update the templates'
    // context to reflect the new object.
    changes?.forEachIdentityChange((record: IterableChangeRecord<T>) => {
      const newData = record.item;
      if (record.currentIndex != undefined) {
        const view = viewContainer.get(record.currentIndex);
        (view as EmbeddedViewRef<any>).context.$implicit = newData;
      }
    });

    // Note: we only `detectChanges` from a top-level call, otherwise we risk overflowing
    // the call stack since this method is called recursively (see #29733.)
    // TODO: change to `this._changeDetectorRef.markForCheck()`,
    // or just switch this component to use signals.
    if (parentData) {
      this._changeDetectorRef.markForCheck();
    } else {
      this._changeDetectorRef.detectChanges();
    }
  }

  /**