<html> <head> <style> .hmmessage P { margin:0px; padding:0px } body.hmmessage { FONT-SIZE: 10pt; FONT-FAMILY:Tahoma } </style> </head> <body class='hmmessage'>Hi Simon: > On Tue, 15 Apr 2008 at 12:36:30 +0000, Robert Rawlins wrote: > > After reading through the tutorial documentation found here http://dbus.freedesktop.org/doc/dbus-tutorial.html it seems that when calling a method which is published as a dbus service that method must _always_ return a value. Is that correct? What if the method which is called doesn't return a value? can I return a VOID value to save upsetting dbus? > > D-Bus methods (should) always return a success or failure message. The > success message may contain 0 or more return values; the failure message > may contain anything, although traditionally it contains a string. > So, a "void" D-Bus method would be one where the success message > contains no return values. > > In dbus-glib APIs, you often end up with a gboolean and a GError ** - on > success, the gboolean is TRUE and the GError is undefined, on failure > the gboolean is FALSE and the GError contains the error - plus an > argument for each argument of the method, and a by-reference (pointer) > argument for each return value of the method. > > For instance, in a "synchronous" service implementation, you always return a > gboolean indicating success or failure. If the method returns something > (say, a string), you'll get a gchar ** argument as well, into which you > must place the returned string on success. Ok, that makes fair sense, I thought that was the case, I now understand that concept. > To return nothing from an asynchronous service implementation (one with > the org.freedesktop.DBus.GLib.Async annotation), > successfully, you'd call dbus_g_method_return (context); where context > is the DBusGMethodInvocation you were given. To return a string you'd > call dbus_g_method_return (context, my_string);. Perfect, this seems like a simple enough implementation, and I use org.freedesktop.DBus.GLib.Async annotation in my current build so that code should drop into place. > The org.freedesktop.DBus.GLib.Const and > org.freedesktop.DBus.GLib.ReturnVal annotations change these rules even > more confusingly. I'd recommend avoiding them. > > Hope this helps, > Simon   I removed my return lines from a method which I no longer wanted to return a value and couldn't figure out why it broke the application but I'm pretty sure that what you've explain here is the reason. I'll try dropping in the dbus_g_method_return (context) snippet into my method a little later and see what effect it has.   Cheers Simon, I'll keep you posted.   Robert <hr />News, Sports, Entertainment and Weather on your mobile. <a href='http://mobile.uk.msn.com/pc/msn_content.aspx' target='_new'>Text MSN to 63463 Now.</a></body> </html>