[systemd-devel] why the function don't have the parameter of 'value'

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Dear all,


I am studying a open source project, and it use the systemd. when I check the property change on dbus, and I found a question, so I sent the email to ask for advice.
when change the property on dbus, it use the function of "sd_bus_emit_properties_changed_strv()" ((systemd\src\libsystemd\sd-bus\bus-objects.c )). But why the function don't include a parameter of value, it just have bus, path, interface, and property-name.  How does this function know what to change of the property?
    _public_ int sd_bus_emit_properties_changed_strv(
                sd_bus *bus,
                const char *path,
                const char *interface,
                char **names) {


        _cleanup_free_ char *prefix = NULL;
        bool found_interface = false;
        size_t pl;
        int r;
       ......
 }


I am looking forward to your reply.
thanks，


Byron








 
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