product_type.rb

module Types
  # Product schema
  class ProductType < GraphQL::Schema::Object
    # Name of this Type
    graphql_name 'Product'
    
    field :sales_history, [Types::SalesHistoryType],
          null: true,
          resolve: ->(product, args, ctx) {
            days = ctx.irep_node.parent.arguments.days || 7
            since = Date.today - days
            [
              product.department_daily_sales
                     .where('invoiced_on >= ? ', since)
                     .order(:invoiced_on)
            ]
          }
    end
end