# `MishkaGervaz.Form.Types.Field.Relation`
[🔗](https://github.com/mishka-group/mishka_gervaz/blob/v0.0.2/lib/mishka_gervaz/form/types/field/relation.ex#L1)

Relation field type for selecting related records in forms.

Follows the same pattern as `MishkaGervaz.Table.Types.Filter.Relation`.

## Modes
- `:static` - Load all options at once (default, for small datasets)
- `:load_more` - Paginated with "Load more" button
- `:search` - Searchable single select
- `:search_multi` - Searchable multi select

## Examples

    field :site_id, :relation do
      mode :static
      display_field :name
    end

    field :category_id, :relation do
      mode :search_multi
      search_field :name
      min_chars 1
    end

## Why the rendered ids carry the form's id

Every DOM id this type hands the adapter is scoped by the id of the form component that is
rendering it — `:table_id` (the adapter's name for "the scope this control belongs to") comes
from `state_assigns.form_id`, and `:id` comes from the Phoenix form field, which already carries
the form's id. A page may mount two `MishkaGervaz.Form.Web.Live` components whose resources
share a field name — `/admin/dashboard/runtime/medias` mounts one for
`MishkaCmsCore.Runtime.Media` and one for `MishkaCmsCore.Runtime.MediaCategory`, and both have a
`site_id` relation. Scoped only by field name, both would render `search-select--site_id`, and
morphdom — which matches by id before anything else — would be free to patch one form's dropdown
with the other form's markup.

See `MishkaGervaz.Form.Behaviours.FieldType`,
`MishkaGervaz.Form.Types.Field`, and the table-side counterpart
`MishkaGervaz.Table.Types.Filter.Relation`.

# `render_input`

```elixir
@spec render_input(map(), map(), map(), module()) :: Phoenix.LiveView.Rendered.t()
```

Renders the relation field input by building assigns and calling the UI adapter.

Delegates to the appropriate UI adapter function based on mode:
- `:static` → `ui.select/1`, with the empty choice `MishkaGervaz.Form.Types.Field.Select.prompt/1`
  gives the field
- `:search` → `ui.search_select/1`
- `:load_more` → `ui.load_more_select/1`
- `:search_multi` → `ui.multi_select/1`

`ui.select/1` is named after the form field, `form[<field>]`, and shows the field's value in
`field_values`, or the form's value when `field_values` holds none.

# `select_mode?`

```elixir
@spec select_mode?(map()) :: boolean()
```

Whether `field` is a relation drawn as a plain select: `:static`, the default, or a mode this
type does not know.

The select posts its pick with the form's own params, as `form[<field>]`, and
`MishkaGervaz.Form.Web.Events.put_select_picks/2` writes it into `state.field_values` on every
`validate` and `save`.

---

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