title: Scoping HasMany Relations

To show a subset of a has_many relationship, create a new has_many relationship in your model (using the scope argument) and add it to the model's dashboard.

Creating a scoped has_many relationship

Models can define subsets of a has_many relationship by passing a callable (i.e. proc or lambda) as its second argument.

class Customer < ApplicationRecord
   has_many :orders
   has_many :processed_orders, ->{ where(processed: true) }, class_name: "Order"

Since ActiveRecord infers the class name from the first argument, the new has_many relation needs to specify the model using the class_name option.

Add new relationship to dashboard

Your new scoped relation can be used in the dashboard just like the original HasMany. Notice the new field needs to specifiy the class name as an option like you did in the model.

ATTRIBUTE_TYPES = {
  orders: Field::HasMany,
  processed_orders: Field::HasMany.with_options(class_name: 'Order')