Method _getDescendants

src/cdk/tree/tree.ts:904–926

Gets all nested descendants of a given node.

(dataNode: T)

  /** Gets all nested descendants of a given node. */
  private _getDescendants(dataNode: T): Observable<T[]> {
    if (this.treeControl) {
      return observableOf(this.treeControl.getDescendants(dataNode));
    }
    if (this.levelAccessor) {
      const results = this._findChildrenByLevel(
        this.levelAccessor,
        this._flattenedNodes.value,
        dataNode,
        Infinity,
      );
      return observableOf(results);
    }
    if (this.childrenAccessor) {
      return this._getAllChildrenRecursively(dataNode).pipe(
        reduce((allChildren: T[], nextChildren) => {
          allChildren.push(...nextChildren);
          return allChildren;
        }, []),
      );
    }
    throw getTreeControlMissingError();
  }

  /**
   * Gets all children and sub-children of the provided node.