Allow additional fields when attaching

app/controllers/avo/associations_controller.rb

@@ -53,26 +53,25 @@ def new
           query = Avo::ExecutionContext.new(target: @field.attach_scope, query: query, parent: @record).handle
         end
 
+        @extra = if @field.extra.present?
+          Avo::FieldsExecutionContext.new(target: @field.extra, parent: @record)
+            .detect_fields
+            .items_holder
+            .items
+        end
+
         @options = query.all.map do |record|
           [@attachment_resource.new(record: record).record_title, record.id]
         end
       end
     end
 
     def create
-      association_name = BaseResource.valid_association_name(@record, association_from_params)
-
-      if reflection_class == "HasManyReflection"
-        @record.send(association_name) << @attachment_record
-      else
-        @record.send(:"#{association_name}=", @attachment_record)
-      end
-
       respond_to do |format|
-        if @record.save
+        if save_association
           format.html { redirect_back fallback_location: resource_view_response_path, notice: t("avo.attachment_class_attached", attachment_class: @related_resource.name) }
         else
-          format.html { render :new }
+          format.html { redirect_back fallback_location: resource_view_response_path, error: "Attachment unsuccessful" }
         end
       end
     end
@@ -159,5 +158,46 @@ def set_related_authorization
     def association_from_params
       @field&.for_attribute || params[:related_name]
     end
+
+    def save_association
+      association_name = BaseResource.valid_association_name(@record, association_from_params)
+
+      if reflection.instance_of?(ActiveRecord::Reflection::ThroughReflection) && additional_params?
+        join_record.save
+      elsif reflection_class == "HasManyReflection"
+        @record.send(association_name) << @attachment_record
+      else
+        @record.send(:"#{association_name}=", @attachment_record)
+      end
+    end
+
+    def additional_params?
+      additional_params.keys.count >= 1
+    end
+
+    def additional_params
+      params[:fields].except("related_id")
+    end
+
+    def reflection
+      @record.class.reflections.with_indifferent_access[association_from_params]
+    end
+
+    def source_foreign_key
+      reflection.source_reflection.foreign_key
+    end
+
+    def through_foreign_key
+      reflection.through_reflection.foreign_key
+    end
+
+    def join_record_params
+      field_names = Avo::FieldsExecutionContext.new(target: @field.extra, parent: @resource).detect_fields.items.map { |field| field.name.tr(" ", "_").downcase }
+      additional_params.permit(field_names).merge({source_foreign_key => @attachment_record.id, through_foreign_key => @record.id})
+    end
+
+    def join_record
+      reflection.through_reflection.klass.new(join_record_params)
+    end
   end
 end

app/views/avo/associations/new.html.erb

@@ -41,6 +41,9 @@
                 class: input_classes('w-full'),
               }
             %>
+          <% @extra&.each_with_index do |ex, index| %>
+            <%= render(Avo::Items::SwitcherComponent.new(resource: @related_resource, item: ex, index: index + 1, view: @view, form: form, field_component_extra_args: {stacked: true})) %>
+          <% end %>
           </div>
         <% end %>
       </div>

lib/avo/fields/has_base_field.rb

@@ -13,6 +13,7 @@ class HasBaseField < BaseField
       attr_accessor :discreet_pagination
       attr_accessor :hide_search_input
       attr_reader :link_to_child_resource
+      attr_reader :extra
 
       def initialize(id, **args, &block)
         super(id, **args, &block)
@@ -27,6 +28,7 @@ def initialize(id, **args, &block)
         @link_to_child_resource = args[:link_to_child_resource] || false
         @reloadable = args[:reloadable].present? ? args[:reloadable] : false
         @linkable = args[:linkable].present? ? args[:linkable] : false
+        @extra = args[:extra].present? ? args[:extra] : nil
       end
 
       def field_resource