module Arel module Visitors class Visitor def accept object visit object end private DISPATCH = Hash.new do |hash, klass| hash[klass] = "visit_#{(klass.name || '').gsub('::', '_')}" end def dispatch DISPATCH end def visit object send dispatch[object.class], object rescue NoMethodError => e raise e if respond_to?(dispatch[object.class], true) superklass = object.class.ancestors.find { |klass| respond_to?(dispatch[klass], true) } raise(TypeError, "Cannot visit #{object.class}") unless superklass dispatch[object.class] = dispatch[superklass] retry end end end end