# `Narabe.Tree`
[🔗](https://github.com/hattoriai/narabe/blob/v0.1.0/lib/narabe/tree.ex#L1)

A tree's items, flat, as a page shows them: each after its parent, with
its level and its place among its siblings.

`Narabe.Components.tree/1` and `tree_picker/1` take the items as the
database has them, a flat list with a parent id each, in their order
(`Narabe.Ecto.ordered/2`), and lay them out with `rows/2`.

# `row`

```elixir
@type row() :: %{
  item: term(),
  id: term(),
  parent: term(),
  level: pos_integer(),
  index: non_neg_integer(),
  count: pos_integer(),
  children: boolean()
}
```

A row of a tree.

# `rows`

```elixir
@spec rows([term()], keyword()) :: [row()]
```

The rows of a tree, in the order a page shows them: depth first, each
item's children after it, siblings in the order of `items`.

An item whose parent is not among the items is at the top: a tree may
show a branch, or the levels loaded so far.

Options:

  * `:id` - the item's id: a key or a function (`:id`).
  * `:parent` - its parent's id: a key or a function (`:parent_id`).
  * `:children` - whether it has children that are not loaded yet: a key
    or a function, or nil (none). An item with loaded children has
    children either way.

## Examples

    iex> items = [%{id: 1, parent_id: nil}, %{id: 2, parent_id: nil}, %{id: 3, parent_id: 1}]
    iex> for row <- Narabe.Tree.rows(items), do: {row.id, row.level, row.index, row.count, row.children}
    [{1, 1, 0, 2, true}, {3, 2, 0, 1, false}, {2, 1, 1, 2, false}]

---

*Consult [api-reference.md](api-reference.md) for complete listing*