def association(association, options = {}, &block)
options = options.dup
return simple_fields_for(*[association,
options.delete(:collection), options].compact, &block) if block_given?
raise ArgumentError, "Association cannot be used in forms not associated with an object" unless @object
reflection = find_association_reflection(association)
raise "Association #{association.inspect} not found" unless reflection
options[:as] ||= :select
options[:collection] ||= fetch_association_collection(reflection, options)
attribute = build_association_attribute(reflection, association, options)
input(attribute, options.merge(reflection: reflection))
end