Select2 and Tom Select alternative for Rails 8

What it does

avo-advanced_search

Let people find the right record by typing a few letters, instead of scrolling a dropdown with a thousand options in it, and skip wiring Select2 or Tom Select into your Rails 8 forms to get there. Searchable Associations turns the standard <select> on an Avo association field into a search-as-you-type picker: set searchable: true on a belongs_to, has_one, or has_many field and the picker queries records as the user types. It reuses the self.search block already defined on the target resource, so most pickers light up with no extra config.

# app/avo/resources/project.rb
class Avo::Resources::Project < Avo::BaseResource
  def fields
    # Boolean form: reuse the target resource's self.search
    field :user, as: :belongs_to, searchable: true

    # Hash form: full control over the query and each row
    field :members, as: :has_many, searchable: {
      query: -> { query.ransack(name_cont: q).result },
      item: -> { { title: record.name, description: record.email } },
      enabled: -> { current_user.admin? }
    }
  end
end

When you need more control, pass a hash instead of true: a query: proc runs as the user types so you decide exactly which records match, item: shapes each row's title and description, and enabled: can switch searchable mode on per user, falling back to a plain select for everyone else. Polymorphic belongs_to works too, with each type routing to its own resource's search. That is a search input wired to your data, built for large tables and vetted across many apps, so your agent sets one option instead of generating it.

What you get

Search-as-you-type picker that replaces the standard <select> on association fields
Works on belongs_to, has_one, and has_many fields, including polymorphic belongs_to
Boolean form (searchable: true) reuses the self.search block already defined on the target resource
Hash form takes a query: proc that runs as the user types, so you decide exactly which records match
item: proc to render each row's title and description in the dropdown
enabled: boolean or proc to turn searchable mode on or off per user, falling back to a plain select
Show default results before any typing by branching on q.blank? inside the query: proc

Why it pays off

Drop searchable: true on a field and a usable picker ships this afternoon, instead of building autocomplete, debouncing, and a JSON endpoint over a sprint.
It reuses the resource search you already configured, so one definition powers every picker pointing at that record.
It is built for the breadth of real apps, large tables, polymorphic targets, per-user gating, the cases a picker built for one app does not need yet.
Every Avo release makes it better: the picker gains improvements and keeps working through upgrades, and fixes reach your app with bundle update.

Questions

Do I need Select2 or Tom Select for this?

No. The picker ships with the add-on, built on Stimulus, and searches on the server as the user types, so there is no jQuery, no JavaScript package to install, and no JSON endpoint to write. If you need a searchable select in your customer-facing forms, outside your Avo app, Tom Select is still a good choice there.

Does it work on Rails 8?

Yes. Avo 4 and its add-ons run on Rails 8; this site runs on them. The picker is part of Avo's own form, so there is nothing to bridge between your asset pipeline, importmap or jsbundling setup and a third-party select library.

Which association fields can be searchable?

belongs_to, including polymorphic, has_one, has_many and has_and_belongs_to_many, plus the record picker in the attach modal. Each one can reuse the target resource's search or take its own query: for that one field.