Select

The Select field renders a dropdown for choosing a value from a list. Choices can come from a label-to-value mapping, a model enum, or grouped options.

# app/avo/resources/project.rb
field :container_size,
  as: :select,
  options: { "Large container" => "large", "Medium container" => "medium", "Tiny container" => "tiny" }

Supply a choice source for each field; Avo does not infer one from the model. By default, the field allows a single selection and displays labels rather than stored values. It does not add a blank choice unless configured or supplied by a translation.

Define the available choices

Use options to map the labels people see to the values your model stores. An array of strings can also serve as a list where labels and values are identical. For Rails-compatible option structures, see options_for_select.

Compute choices for the current record

If the choices depend on the record or request, use a lambda. It runs in an ExecutionContext with record, resource, view, and field available. Account for new records as well as persisted ones.

# app/avo/resources/project.rb
field :container_size,
  as: :select,
  options: -> do
    { "Large container" => "large", "Medium container" => "medium", "Tiny container" => "tiny" }
  end

The lambda can return an array of label/value pairs when choices come from database records, such as ContainerType.order(:name).pluck(:name, :id) if your application defines that model.

Organize choices into groups

Use grouped_options to break a long list into labeled groups. Both Hash and Array structures accepted by Rails' grouped_options_for_select helper work in the dropdown.

# app/avo/resources/project.rb
field :country,
  as: :select,
  grouped_options: {
    "North America" => [["United States", "US"], ["Canada", "CA"]],
    "Europe" => [["Denmark", "DK"], ["Germany", "DE"], ["France", "FR"]]
  }

Prefer the Hash form when you want index and show views to resolve stored values to labels. With an outer Array, those views display the stored value instead.

# app/avo/resources/project.rb
field :country,
  as: :select,
  grouped_options: [
    ["North America", [["United States", "US"], "Canada"]],
    ["Europe", ["Denmark", "Germany", "France"]]
  ]

Compute grouped choices

If groups change dynamically, provide a lambda returning the same grouped structure. It has the same execution context as computed choices.

# app/avo/resources/project.rb
field :country,
  as: :select,
  grouped_options: -> do
    {
      "North America" => [["United States", "US"], ["Canada", "CA"]],
      "Europe" => [["Denmark", "DK"], ["Germany", "DE"], ["France", "FR"]]
    }
  end

Choose one source

Use only one of options, grouped_options, or enum per field. Avo does not reject conflicting sources, and they can produce inconsistent dropdown and display values.

Use a model enum

Pass your Active Record enum mapping to enum. Avo uses enum keys as submitted values so Rails can assign the attribute.

# app/models/project.rb
class Project < ApplicationRecord
  enum :container_size, { large: "large", medium: "medium", tiny: "small" }
end

# app/avo/resources/project.rb
field :container_size,
  as: :select,
  enum: ::Project.container_sizes,
  display_value: true,
  placeholder: "Choose the type of the container.",
  include_blank: true

Display stored values instead of labels

Set display_value to show the values from a Hash instead of its labels. For example, the first example would display large rather than Large container, in both the dropdown and read-only views. This does not change which value the field stores.

For an enum, it displays the mapped value (small in the enum example) instead of the enum key (tiny). Array choices ignore this setting. See the reference for grouped-choice behavior.

Let users clear a selection

Set include_blank to true to add an empty-valued choice labeled with the field's placeholder. Without a custom placeholder or translation, the label is "Choose an option". Supply a string instead to give the blank choice its own label.

# app/avo/resources/project.rb
field :container_size,
  as: :select,
  options: { "Large container" => "large", "Tiny container" => "tiny" },
  include_blank: "No type"

Whether an empty value is persisted as an empty string or nil depends on your model's attribute type and application logic. A placeholder alone does not add a blank choice.

Allow more than one selection

Enable multiple when the model attribute accepts an array of values. Ensure your model can persist that array, for example with a PostgreSQL array column. Avo removes blank entries on submission.

# app/avo/resources/project.rb
field :categories,
  as: :select,
  options: { "News" => "news", "Tutorials" => "tutorials" },
  multiple: true

Common field options

For labels, visibility, placeholders, and other shared settings, see Common field options.