https://github.com/orgsync/active_interaction/issues/247

orgsync-active_interaction-247.rb

# coding: utf-8

require 'active_interaction' # 1.4.1
require 'active_record' # 4.2.0
require 'sqlite3' # 1.3.10

ActiveRecord::Base.establish_connection(
  adapter: 'sqlite3', database: ':memory:')

ActiveRecord::Schema.define do
  create_table :cars

  create_table :wheels do |table|
    table.column :car_id, :integer
  end
end

class Car < ActiveRecord::Base
  has_many :wheels
end

class Wheel < ActiveRecord::Base
  belongs_to :car
end

class CountWheels < ActiveInteraction::Base
  array :wheels

  def execute
    wheels.size
  end
end

car = Car.create!
car.wheels.create!
inputs = { wheels: car.wheels }
inputs[:wheels].class
# => Wheel::ActiveRecord_Associations_CollectionProxy
CountWheels.run!(inputs)
# => 1