# جدول البيانات: الصفوف الشجرية

> Show nested rows in the slotsmith data table with getSubRows, and control which rows are expanded.

The data table shows nested rows when you pass `getSubRows`, a function that returns a row's children. Rows with children get an expand toggle in their first cell, and each level is indented. Pass `expanded` with `onExpandedChange` to control which rows are open.

```tsx
import { useState } from "react";
import { DataTable, type DataTableColumnDef, type DataTableExpandedState } from "slotsmith/data-table";

type Unit = { id: string; name: string; lead: string; headcount: number; units?: Unit[] };

const company: Unit[] = [
  {
    id: "eng",
    name: "Engineering",
    lead: "Yuki Tanaka",
    headcount: 42,
    units: [
      {
        id: "eng-platform",
        name: "Platform",
        lead: "Lena Park",
        headcount: 18,
        units: [
          { id: "eng-platform-infra", name: "Infrastructure", lead: "Diego Alvarez", headcount: 10 },
          { id: "eng-platform-tools", name: "Developer tools", lead: "Sofia Reyes", headcount: 8 },
        ],
      },
      { id: "eng-payments", name: "Payments", lead: "Chloe Martin", headcount: 24 },
    ],
  },
  {
    id: "product",
    name: "Product",
    lead: "Omar Haddad",
    headcount: 15,
    units: [
      { id: "product-design", name: "Design", lead: "Priya Nair", headcount: 9 },
      { id: "product-research", name: "Research", lead: "Amir Nasser", headcount: 6 },
    ],
  },
  { id: "care", name: "Customer care", lead: "Hana Kim", headcount: 12 },
];

const columns: DataTableColumnDef<Unit>[] = [
  // The first column holds the expand toggle and is indented by depth.
  { accessorKey: "name", header: "Unit" },
  { accessorKey: "lead", header: "Lead" },
  { accessorKey: "headcount", header: "People", meta: { align: "end" } },
];

export default function TreeRows() {
  const [expanded, setExpanded] = useState<DataTableExpandedState>({});
  const open = expanded === true ? "all" : Object.keys(expanded).filter((id) => expanded[id]);
  return (
    <>
      <DataTable
        data={company}
        columns={columns}
        getRowId={(unit) => unit.id}
        // Each row's children: rows with any become expandable.
        getSubRows={(unit) => unit.units}
        expanded={expanded}
        onExpandedChange={setExpanded}
        enablePagination={false}
      />
      <p>{open.length === 0 ? "Every row is collapsed." : `Expanded: ${open === "all" ? "all" : open.join(", ")}`}</p>
    </>
  );
}
```

Open Engineering, then Platform, to see two levels of sub-rows. The text under the table lists the expanded rows by id.

## Sub-rows

[`getSubRows`](https://slotsmith.dev/ar/components/data-table/api/#props) receives each row and returns its children, or `undefined` for a leaf. The children use the same columns as their parent. Give every row, at every level, an id with [`getRowId`](https://slotsmith.dev/ar/components/data-table/api/#props), so the expanded state, the selection and a [row reorder](https://slotsmith.dev/ar/components/data-table/guides/row-reorder/) follow the row and not its position.

For children that load later, [`getRowCanExpand`](https://slotsmith.dev/ar/components/data-table/api/#props) decides which rows show a toggle before their children arrive; fetch the children when the row expands and put them in `data`.

## Expanded state

- [`expanded`](https://slotsmith.dev/ar/components/data-table/api/#props) and [`onExpandedChange`](https://slotsmith.dev/ar/components/data-table/api/#props) control it, as the demo does. The state is `{ [rowId]: true }` for the open rows, or `true` for every row.
- [`defaultExpanded`](https://slotsmith.dev/ar/components/data-table/api/#props) sets a starting state the table keeps itself, such as `{ eng: true }` or `true` to open everything.
- [`paginateExpandedRows`](https://slotsmith.dev/ar/components/data-table/api/#props) counts sub-rows towards the page size. By default only top-level rows count, so a page keeps its parents' children with it.

## The parts

The toggle is the [`ExpandToggle`](https://slotsmith.dev/ar/components/data-table/api/#slot-ExpandToggle) slot: a `<button>` with `aria-expanded`, named by the [`expandRow`](https://slotsmith.dev/ar/components/data-table/api/#label-expandRow) or [`collapseRow`](https://slotsmith.dev/ar/components/data-table/api/#label-collapseRow) label. It receives `expanded`, `depth` and `onToggle`, and a click on it does not run `onRowClick`. A row with no children gets a spacer in its place, so the names line up. The built-in toggle also sets an empty `data-expanded` on itself while open, which its stylesheet uses to turn the chevron; a toggle of your own gets `expanded` and sets whatever it needs.

Each [`Row`](https://slotsmith.dev/ar/components/data-table/api/#slot-Row) carries `data-depth` (`0` for top-level rows) and, when it can expand, `data-expanded` (`"true"` or `"false"`), so a stylesheet can mark the levels.