<div dir="ltr">I'll use this way as a solution. Thank you very much. </div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Jan 28, 2023 at 11:22 PM Robert Middleton <<a href="mailto:robert.middleton@rm5248.com">robert.middleton@rm5248.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">DBus methods are similar to C in that all defined arguments are required to methods. It is possible that specific implementations/language bindings may allow you to have default values, but that is not something that I am aware of. If you have optional arguments, the best way to implement that would be to send a map<string,variant>(or a{sv} in dbus-speak) that lets you test for arguments that may or may not exist. This mechanism is used by DBus itself for messages, as well as some standard services like the org.freedesktop.Notifications[1]. -Robert Middleton [1]: <a href="https://specifications.freedesktop.org/notification-spec/notification-spec-latest.html" rel="noreferrer" target="_blank">https://specifications.freedesktop.org/notification-spec/notification-spec-latest.html</a> On Sat, Jan 28, 2023 at 7:01 AM Charles Wong <<a href="mailto:ymqiuyu@gmail.com" target="_blank">ymqiuyu@gmail.com</a>> wrote: > > Hi, > > Is this the right place to ask dbus questions? > > For example, there is a dbus config (is from <a href="https://gjs.guide/guides/gio/dbus.html#high-level-proxies" rel="noreferrer" target="_blank">https://gjs.guide/guides/gio/dbus.html#high-level-proxies</a>): > ```xml > <method name="ComplexMethod"> > <arg type="b" direction="in" name="input"/> > <arg type="u" direction="out" name="length"/> > </method> > ``` > > Is it possible to set a default value to parameter `input` and mark it as unrequired? > > Just like in spring mvc, we can set a parameter `required=false` and set `default` value too: > `@RequestParam(required = false, defaultValue = "default value") String parameter` </blockquote></div>