class ActiveFedora::Associations::Builder::Contains

def self.define_readers(mixin, name)
  mixin.send(:define_method, name) do |*params|
    association(name).reader(*params).tap do |file|
      set_uri = uri.kind_of?(RDF::URI) ? uri.value.present? : uri.present?
      if set_uri
        file_uri = "#{uri}/#{name}"
        file.uri = file_uri
        file.exists! if contains_assertions.include?(file_uri)
      end
    end
  end
end

def initialize(model, name, options)
  super
  options[:class_name] = 'ActiveFedora::File' if options[:class_name].blank?
end

def validate_options
  super
  if options[:class_name] && !options[:class_name].is_a?(String)
    raise ArgumentError, ":class_name must be a string for contains '#{name}'" unless options[:class_name].is_a? String
  end
end