Administrate::Field::LazyBelongsTo

An input field that shows search results of an association, lazily.

Add this line to your application's Gemfile:

gem 'administrate-field-lazy_belongs_to'

And then execute:

$ bundle

Or install it yourself as:

$ gem install administrate-field-lazy_belongs_to

This field needs a bit of setup, unless you're using XPBytes/administrate-base_controller, in order to lazily collect the values you're looking for. If you are using the BaseController, you only need to set-up the fields.

You need to have a route that yields an array of objects with at least the value and label you want to show. The best way is to re-use everything administrate offers you, which is the default behaviour of Administrate::BaseController:

class BookController < Admin::ApplicationController
  def index
    respond_to do |format|
      format.json do
        resources = Administrate::Search.new(scoped_resource, dashboard_class, params[:search].to_s.strip).run
        resources = apply_resource_includes(resources)
        resources = order.apply(resources)
        resources = resources.page(params[:page]).per(records_per_page)

        render json: resources
      end

      format.any { super }
    end
  end
end

This way, your already existing route also is available in JSON. You may optimize this by only use the id and value field: resources.to_json(fields: %i[id name]).

You could also use the dashboard display:

render json: resources.map do |resource| 
  { id: resource.id, name: dashboard.display_resource(resource) }
end

The rest of the setup is as easy as any other field, except that you need to tell the field where to query the results, which key it should use for the value (defaults to id) and the label (defaults to name).

require "administrate/base_dashboard"

class BookDashboard < Administrate::BaseDashboard
  # ATTRIBUTE_TYPES
  # a hash that describes the type of each of the model's fields.
  #
  # Each different type represents an Administrate::Field object,
  # which determines how the attribute is displayed
  # on pages throughout the dashboard.
  ATTRIBUTE_TYPES = {
    id: Field::String,
    name: Field::String,
    author: Field::LazyBelongsTo.with_options(
      placeholder: 'Select the author',
      action: ->(field, q:) { field.url_helpers.admin_publisher_books_path(field.resource.publisher, search: q) },
      value_attribute: :id,
      label_attribute: :name
    ),
    created_at: Field::DateTime,
    updated_at: Field::DateTime
  }.freeze
  
  # ...
end

You get the field and the search template q as argument and named argument. By default this is {q} which is replaced with the actual query on the front-end. You can use the field.resource shortcut to scope the url; in this example above it will only show authors with the current publisher.

• Administrate: A Rails engine that helps you put together a super-flexible admin dashboard.
• Administrate::BaseController: 🌠 A set of application controller improvements.

• Administrate::DefaultOrder: 🔢 Sets the default order for a resource in a administrate controller.
• Administrate::SerializedFields: 🆎 Automatically deserialize administrate fields on form submit.

• Administrate::Field::Code: 📝 A text field that shows code.
• Administrate::Field::Hyperlink: 📝 A string field that is shows a hyperlink.
• Adminisrtate::Field::JsonEditor: 📝 A text field that shows a JSON editor.
• Administrate::Field::ScopedBelongsTo: 📝 A belongs_to field that yields itself to the scope lambda.
• Administrate::Field::ScopedHasMany: 📝 A has_many field that yields itself to the scope lambda.
• Administrate::Field::TimeAgo: 📝 A date_time field that shows its data as time_ago since.

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at XPBytes/administrate-field-lazy_belongs_to.