注册本地回调函数时如何应用reflect

reg_reflect.go

func (server *Server) Register(rcvr interface{}) error {
	s := new(service)
	s.typ = reflect.TypeOf(rcvr)
	s.rcvr = reflect.ValueOf(rcvr)
	sname := reflect.Indirect(s.rcvr).Type().Name()
	if sname == "" {
		s := "rpc.Register: no service name for type " + s.typ.String()
		log.Print(s)
		return errors.New(s)
	}
	if !isExported(sname) {
		s := "rpc.Register: type " + sname + " is not exported"
		log.Print(s)
		return errors.New(s)
	}
	if _, present := server.serviceMap[sname]; present {
		return errors.New("rpc: service already defined: " + sname)
	}
	s.name = sname
	// Install the methods
	s.method = suitableMethods(s.typ, true)
	if len(s.method) == 0 {
		str := ""
		// To help the user, see if a pointer receiver would work.
		method := suitableMethods(reflect.PtrTo(s.typ), false)
		if len(method) != 0 {
			str = "rpc.Register: type " + sname + " has no exported methods of suitable type (hint: pass a pointer to value of that type)"
		} else {
			str = "rpc.Register: type " + sname + " has no exported methods of suitable type"
		}
		log.Print(str)
		return errors.New(str)
	}
	server.serviceMap[s.name] = s
	return nil
}

// suitableMethods returns suitable Rpc methods of typ, it will report
// error using log if reportErr is true.
func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {
	methods := make(map[string]*methodType)
	for m := 0; m < typ.NumMethod(); m++ {
		method := typ.Method(m)
		mtype := method.Type
		mname := method.Name
		// Method must be exported.
		if method.PkgPath != "" {
			continue
		}
		// Method needs three ins: receiver, *args, *reply.
		if mtype.NumIn() != 3 {
			if reportErr {
				log.Println("method", mname, "has wrong number of ins:", mtype.NumIn())
			}
			continue
		}
		// First arg need not be a pointer.
		argType := mtype.In(1)
		if !isExportedOrBuiltinType(argType) {
			if reportErr {
				log.Println(mname, "argument type not exported:", argType)
			}
			continue
		}
		// Second arg must be a pointer.
		replyType := mtype.In(2)
		if replyType.Kind() != reflect.Ptr {
			if reportErr {
				log.Println("method", mname, "reply type not a pointer:", replyType)
			}
			continue
		}
		// Reply type must be exported.
		if !isExportedOrBuiltinType(replyType) {
			if reportErr {
				log.Println("method", mname, "reply type not exported:", replyType)
			}
			continue
		}
		// Method needs one out.
		if mtype.NumOut() != 1 {
			if reportErr {
				log.Println("method", mname, "has wrong number of outs:", mtype.NumOut())
			}
			continue
		}
		// The return type of the method must be error.
		if returnType := mtype.Out(0); returnType != typeOfError {
			if reportErr {
				log.Println("method", mname, "returns", returnType.String(), "not error")
			}
			continue
		}
		methods[mname] = &methodType{method: method, ArgType: argType, ReplyType: replyType}
	}
	return methods
}