Net::HTTP回りを調べる

require "net/http"
list = []
Net.constants.sort.each do |c|
    next unless /^H/.match c
    sc = Net.const_get(c).ancestors rescue 'Module'
    list << sc.select { |e| /Object|Kernel/ !~ e.to_s }.reverse
end

list.sort_by { |e| e.length }.uniq.each { |e| puts e.join ' < ' }

出力

Net::HTTPExceptions
Net::HTTPHeader
Net::Protocol < Net::HTTP
Net::HTTPHeader < Net::HTTPResponse
Net::HTTPHeader < Net::HTTPGenericRequest
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPServerError
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError
Net::HTTPHeader < Net::HTTPGenericRequest < Net::HTTPRequest
Exception < StandardError < Net::HTTPBadResponse
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPInformation
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPUnknownResponse
Exception < StandardError < Net::HTTPHeaderSyntaxError
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPServerError < Net::HTTPNotImplemented
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPServerError < Net::HTTPInternalServerError
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPLengthRequired
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPMethodNotAllowed
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection < Net::HTTPMovedPermanently
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection < Net::HTTPFound
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection < Net::HTTPMultipleChoice
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess < Net::HTTPNoContent
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess < Net::HTTPNonAuthoritativeInformation
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPNotAcceptable
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPNotFound
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPGone
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection < Net::HTTPNotModified
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess < Net::HTTPOK
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess < Net::HTTPPartialContent
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPPaymentRequired
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPPreconditionFailed
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPProxyAuthenticationRequired
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPServerError < Net::HTTPGatewayTimeOut
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPForbidden
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPRequestEntityTooLarge
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPRequestTimeOut
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPUnauthorized
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPRequestURITooLong
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPRequestedRangeNotSatisfiable
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess < Net::HTTPResetContent
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPServerError < Net::HTTPVersionNotSupported
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPExpectationFailed
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection < Net::HTTPUseProxy
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPUnsupportedMediaType
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection < Net::HTTPSeeOther
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess < Net::HTTPCreated
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPInformation < Net::HTTPContinue
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPSuccess < Net::HTTPAccepted
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPServerError < Net::HTTPServiceUnavailable
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPConflict
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPClientError < Net::HTTPBadRequest
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPServerError < Net::HTTPBadGateway
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPInformation < Net::HTTPSwitchProtocol
Net::HTTPHeader < Net::HTTPResponse < Net::HTTPRedirection < Net::HTTPTemporaryRedirect
Exception < StandardError < Net::ProtocolError < Net::HTTPExceptions < Net::HTTPError
Exception < StandardError < Net::ProtocolError < Net::ProtoServerError < Net::HTTPExceptions < Net::HTTPServerException
Exception < StandardError < Net::ProtocolError < Net::ProtoRetriableError < Net::HTTPExceptions < Net::HTTPRetriableError
Exception < StandardError < Net::ProtocolError < Net::ProtoFatalError < Net::HTTPExceptions < Net::HTTPFatalError