Ability to attach models when creating parent models.

[adrianthedev]

If you have a User model that has_many Posts you might want to attach some posts when creating the User model.

Right now you have to first sane the User and then attach the other models in the Show screen.

[notnotdrew]

Assuming the Posts already exist, we've used AR associations helpers (i.e. User#post_ids) and a custom multi-select field to accomplish this; e.g.

class User < ActiveRecord::Base
  has_many :user_posts
  has_many :posts, through: :user_posts
end

# ... assume similar/necessary set up for `UserPost` & `Post`

class UserResource < Avo::BaseResource
  field :posts, as: :has_many
  
  field :post_ids, as: :multi_select, name: 'Posts', only_on: [:forms], options: ->(_) { Post.pluck(:title, :id) }
end

[notnotdrew]

Our use case was a many-to-many, so that's what I've modeled here, but I think it could work for one-to-many as well? 🤔

[adrianthedev]

It would be interesting to see that multi_select field. We'll bring in plugins in the future so you can easily plug-in custom fields.

[notnotdrew]

That'd be super cool! We basically copied the existing select field with minor tweaks to allow multi-select. The highlights of that are:

<%# app/components/avo/fields/multiselect_field/edit_component.html.erb %>

<%= edit_field_wrapper field: @field, index: @index, form: @form, resource: @resource, displayed_in_modal: @displayed_in_modal do %>
  <%= @form.select @field.id, @field.options_for_select, {
      selected: @field.value, prompt: @field.placeholder
    }, {
      class: helpers.input_classes(' w-full', has_error: @field.model_errors.include?(@field.id)),
      disabled: @field.readonly,
      multiple: true,
      value: @field.model.present? ? @field.model[@field.id] : @field.value
    }
  %>
<% end %>

# app/avo/fields/multi_select_field.rb

class MultiSelectField < Avo::Fields::BaseField
  def initialize(name, **args, &block)
    args[:placeholder] ||= 'Select an option (or multiple)'

    super(name, **args, &block)

    options = args.fetch(:options)

    @options = options.is_a?(Hash) ? options.with_indifferent_access : options
  end

  def options_for_select
    options =
      if @options.respond_to? :call
        @options.call(model: model, resource: resource, view: view, field: self)
      else
        @options
      end

    options.sort_by { |key, _| key }.to_h
  end

  def label
    # Uses a comma separated list on show page, etc
    options_for_select.invert.stringify_keys.values_at(*value).compact.sort.join(', ')
  end

  def to_permitted_param
    { id.to_sym => [] }
  end

  # NOTE: #value was copied out of Avo::BaseField (v1.17.0) to address an issue when :new is rendered after a failed create.
  # As defined in BaseField, the multi-select values were cleared rather than persisted as they should be.
  def value(property = nil)
    property ||= id

    # Get model value
    final_value = @model.send(property) if (model_or_class(@model) == "model") && @model.respond_to?(property)

    # >>> NOTE: this is the change to address the issue noted above.
    # if (@view === :new) || @action.present?
    if final_value.blank? && ((@view === :new) || @action.present?)
    # <<<
      final_value = if default.present? && default.respond_to?(:call)
        default.call
      else
        default
      end
    end

    # Run callback block if present
    if computable && block.present?
      final_value = block.call @model, @resource, @view, self
    end

    # Run the value through resolver if present
    final_value = @format_using.call final_value if @format_using.present?

    final_value
  end
end

[adrianthedev]

That's amazing. Thanks for sharing!