api_creatable.rb

module ShopProductSink
  module ApiCreatable
    extend ActiveSupport::Concern

    module ClassMethods
      def initialize_from_resource(resource)
        attributes = usable_keys.reduce({}) do |result, key|
          result[key] = resource.public_send(key) if resource.respond_to?(key)
          result
        end
        record = self.new(attributes)
        reflect_on_all_associations.each do |association|
          if resource.respond_to?(association.name)
            resource_or_resources = resource.public_send(association.name)
            records = association.active_record.initialize_from_resources(resource_or_resources)
            record.public_send("#{association.name}=", association.collection? ? records : records.first)
          end
        end
      end

      def initialize_from_resources(resources)
        Array[*resources].map { |resource| initialize_from_resource(resource) }
      end

      def create_from_resource(resource)
        initialize_from_resource(resource).save
      end

      def create_from_resources(resources)
        Array[*resources].map { |resource| create_from_resource(resource) }
      end

      def usable_keys
        columns.map(&:name)
      end
    end
  end
end

api_creatable_test.rb

require 'test_helper'

module ShopProductSink
  class ApiCreatableTest < ShopProductSink::UnitTest
    attr_reader :resource
    
    test "it should be possible to find initialize all relations for the object" do
      integration_object_relations_resources = [new_resource(id: 1, integration_object_id: 1, sku: 'saucey', option1: 'red')]
      resource = new_resource(integration_object_relations: integration_object_relations_resources)
      object = IntegrationObject.initialize_from_resource(resource)
      assert_equal 1, object.integration_object_relations.size
      relation = object.integration_object_relations.first
      assert_equal object.id, relation.integration_object_id
    end
    
    private
    def new_resource(options={})
      defaults = {id: 1, title: 'Fox', price: '12.00'}.merge(options)
      ShopifyAPI::Product.new(defaults)
    end
  end
end

test_failure.out

  1) Error:
ShopProductSink::ApiCreatableTest#test_it_should_be_possible_to_find_initialize_all_relations_for_the_object:
NameError: uninitialized constant IntegrationObjectRelation
    activesupport (4.0.2) lib/active_support/inflector/methods.rb:226:in `const_get'
    activesupport (4.0.2) lib/active_support/inflector/methods.rb:226:in `block in constantize'
    activesupport (4.0.2) lib/active_support/inflector/methods.rb:224:in `each'
    activesupport (4.0.2) lib/active_support/inflector/methods.rb:224:in `inject'
    activesupport (4.0.2) lib/active_support/inflector/methods.rb:224:in `constantize'
    activesupport (4.0.2) lib/active_support/core_ext/string/inflections.rb:66:in `constantize'
    activerecord (4.0.2) lib/active_record/associations/association.rb:222:in `raise_on_type_mismatch!'
    activerecord (4.0.2) lib/active_record/associations/collection_association.rb:333:in `block in replace'
    activerecord (4.0.2) lib/active_record/associations/collection_association.rb:333:in `each'
    activerecord (4.0.2) lib/active_record/associations/collection_association.rb:333:in `replace'
    activerecord (4.0.2) lib/active_record/associations/collection_association.rb:42:in `writer'
    activerecord (4.0.2) lib/active_record/associations/builder/association.rb:78:in `integration_object_relations='
    /home/vagrant/src/shopProductSink/app/models/shop_product_sink/api_creatable.rb:16:in `public_send'
    /home/vagrant/src/shopProductSink/app/models/shop_product_sink/api_creatable.rb:16:in `block in initialize_from_resource'
    /home/vagrant/src/shopProductSink/app/models/shop_product_sink/api_creatable.rb:12:in `each'
    /home/vagrant/src/shopProductSink/app/models/shop_product_sink/api_creatable.rb:12:in `initialize_from_resource'
    test/models/shop_product_sink/api_creatable_test.rb:61:in `block in <class:ApiCreatableTest>'
    minitest (4.7.5) lib/minitest/unit.rb:1258:in `run'
    minitest (4.7.5) lib/minitest/unit.rb:933:in `block in _run_suite'
    minitest (4.7.5) lib/minitest/unit.rb:926:in `map'
    minitest (4.7.5) lib/minitest/unit.rb:926:in `_run_suite'
    minitest (4.7.5) lib/minitest/parallel_each.rb:71:in `block in _run_suites'
    minitest (4.7.5) lib/minitest/parallel_each.rb:71:in `map'
    minitest (4.7.5) lib/minitest/parallel_each.rb:71:in `_run_suites'
    minitest (4.7.5) lib/minitest/unit.rb:877:in `_run_anything'
    minitest (4.7.5) lib/minitest/unit.rb:1085:in `run_tests'
    minitest (4.7.5) lib/minitest/unit.rb:1072:in `block in _run'
    minitest (4.7.5) lib/minitest/unit.rb:1071:in `each'
    minitest (4.7.5) lib/minitest/unit.rb:1071:in `_run'
    minitest (4.7.5) lib/minitest/unit.rb:1059:in `run'
    minitest (4.7.5) lib/minitest/unit.rb:795:in `block in autorun'