Field Discovery API

Per-option reference for discover_columns and discover_associations. For task-oriented documentation and worked examples, see the Field Discovery guide.

Both methods are called inside a resource's fields method and share the same signature:

def fields
  discover_columns only: [], except: [], **field_options
  discover_associations only: [], except: [], **field_options
end

discover_columns handles database columns, rich text bodies (has_rich_text), and tags (acts_as_taggable_on). discover_associations handles attachments (has_one_attached / has_many_attached) and regular Active Record associations.

Method options

-> only

Discover only the listed columns or associations, excluding all others.

discover_columns only: [:title, :body, :published_at]

• Type: Array of Symbols — column or association names
• Default: nil (everything is discovered)

-> except

Discover everything except the listed columns or associations.

discover_columns except: [:metadata, :internal_notes]

• Type: Array of Symbols — column or association names
• Default: nil (nothing is excluded)

-> field_options

Any other keyword argument is forwarded verbatim to every field the call discovers.

discover_columns help: "Automatically discovered"
discover_associations searchable: false

• Type: keyword arguments, same options a manual field declaration accepts
• Default: none

Discovery behavior

Mapping precedence

Each column's field configuration is resolved by the first match, in order:

1. The model's Rails enums — rendered as a select field with the enum's values.
2. column_names_mapping — matched on column name.
3. column_types_mapping — matched on database column type.

Columns with no match in any of the three are not discovered.

Ignored columns

These columns are never discovered, regardless of only:

encrypted_password, reset_password_token, reset_password_sent_at, remember_created_at, password_digest

Columns that back an association, a rich text body, or an attachment are also skipped by discover_columns so a field isn't generated twice.

Association defaults

Discovered associations receive searchable: true and sortable: true. Polymorphic belongs_to associations get polymorphic_as and a types array detected from the models on the other side of the association.

Global configuration

Both options live in the initializer and apply to every resource that uses discovery. They merge on top of the default mappings, so list only the entries you want to add or change. In each entry, field names the field type and every other key is passed to the field as options.

-> column_names_mapping

Overrides the field configuration for specific column names.

config.column_names_mapping = {
  published_at: {field: :date_time},
  body: {field: :markdown}
}

• Type: Hash — column name (Symbol) → field configuration Hash
• Default: {} (the built-in name mappings still apply)

-> column_types_mapping

Overrides the field configuration for database column types.

config.column_types_mapping = {
  jsonb: {field: :code, language: "json"}
}

• Type: Hash — column type (Symbol) → field configuration Hash
• Default: {} (the built-in type mappings still apply)

Default mappings

The tables below mirror lib/avo/mappings.rb.

Column names

Column name	Field
id	id
description	textarea
gravatar	gravatar
email	text
password, password_confirmation	password
stage	select
budget, money	currency
country	country

Column types

Column type	Field
primary_key	id
string	text
text	textarea
integer, float, decimal, binary	number
datetime, timestamp, time	date_time
date	date
boolean	boolean
references, belongs_to	belongs_to
json, jsonb	code

Associations

Association	Field	Discovered by
belongs_to	belongs_to	discover_associations
has_one	has_one	discover_associations
has_many	has_many	discover_associations
has_and_belongs_to_many	has_and_belongs_to_many	discover_associations
has_one_attached	file	discover_associations
has_many_attached	files	discover_associations
has_rich_text	trix	discover_columns
acts_as_taggable_on	tags	discover_columns