gistfile1.rb

class ExternalResourcePersister
  attr_reader :record, :resource

  def initialize( resource, record = nil )
    @resource = resource
    @record   = record
  end


  def create!
    raise ActiveResource::ResourceInvalid if !resource.valid?
    record_attrs = record_attributes

    record_class.create!(record_attrs)
  end

  def update!
    record_attrs = record_attributes
    record       = record_class.find_by(remote_id: record_attrs[:remote_id]) unless record
    
    record.update!(record_attrs)
    record
  end

  def create_or_update!
    if record_class.find_by(remote_id: resource.id) 
      update!
    else
      create!
    end    
  end

protected
  def record_attributes
    record_attrs             = resource.attributes.clone
    record_attrs[:remote_id] = record_attrs.delete(:id)
    record_attrs.reject{|k,v| !record_class.new.attributes.keys.member?(k.to_s) }
  end

  def record_class
    resource.class.name.demodulize.constantize
  end
end