# `MishkaGervaz.Form.Types.Field.Nested`
[🔗](https://github.com/mishka-group/mishka_gervaz/blob/v0.0.6/lib/mishka_gervaz/form/types/field/nested.ex#L1)

Nested / embedded form field type, used for `inputs_for` and constrained-map columns.

## Example

    field :seo_tags, :nested do
      ui do
        add_label "+ Add SEO tag"
        remove_label "Remove"
      end

      nested_field :tag do
        ui do placeholder "meta, link, script" end
      end

      nested_field :content, :textarea do
        ui do rows 3 end
      end
    end

## Sub-field values are cast on the way in

`parse_params/2` casts each row by its sub-field's declared type before the value reaches the
changeset:

| Sub-field type        | Cast                                                        |
|-----------------------|-------------------------------------------------------------|
| `:checkbox`, `:toggle`| `"true"` / `"on"` / `"1"` to `true`; `"false"` / `"off"` / `"0"` / `""` to `false` |
| `:number`             | integer, then float                                          |
| `:key_map`            | each declared key cast, then blanks dropped                  |
| `:key_list`           | each row cast and pruned, then empty rows dropped            |

Anything it cannot make sense of is left exactly as it came, and a value that is already the
right type passes through untouched.

See `MishkaGervaz.Form.Behaviours.FieldType` and `MishkaGervaz.Form.Types.Field`.

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