This post is a "things that should be easily googleable but aren't" type post.

When an application is returning a dbus array of integers (Dbus type 'ai'), qdbusviewer will give you a message similar to:

unable to find method <MethodName> on path <DbusPath> in interface <Interface>

This message is sign of a failing in qdbusviewer and not in the application (as I discovered to today after a couple of hours of confusion!)

The solution is to use another dbus client, for example:

$ dbus-send --session --type=method_call --print-reply --dest=<Interface> <DbusPath> <MethodName>
method return sender=:1.165 -> dest=:1.171 reply_serial=2
array [       int32 0       int32 1    ]

Hopefully that will save someone some pain.