On Tuesday, November 19, 2019 at 11:21:17 AM UTC-5, Ken Bassford wrote:
>
> Hi Folks,
>
> I have been trying to implement godbus's Export function to no avail.
> Looking at server.go (under the examples folder) is not very helpful as an
> inspection of export.go contains what appear to be cheater functions that
> enable the example to work. Rename "Foo" to "Ping and it fails.
>
> With that out of the way, I have not been able to find any current
> projects that utilize godbus server functions as a good example (I'm
> readily open to suggestions). Snippets of what I currently have are as
> follows ...
>
> First I created a structure to server as a basis for follow-on functions
> (since you can't expand *dbus.Conn as it is predefined in another package)
> ...
> ```
> type dbusobj struct {
> Conn *dbus.Conn
> Iface string
> Path dbus.ObjectPath
> }
> ```
> .. a function to populate the structure ...
> ```
> func newDbusObject(conn *dbus.Conn, iface string, path dbus.ObjectPath)
> dbusobj {
> pdbo := new(dbusobj)
> pdbo.Conn = conn
> pdbo.Iface = iface
> pdbo.Path = path
> return *pdbo
> }
> ```
> ... and a simple function to export a named method interface ...
> ```
> func (co dbusobj) addResponseMethod(methodname string) error {
> var methodxml = `
> <node>
> <interface name="` + co.Iface + `">
> <method name="` + methodname + `">
> <arg direction="out" type="s"/>
> </method>
> </interface>` + introspect.IntrospectDataString +
> `</node>`
> return co.Conn.Export(introspect.Introspectable(methodxml), co.Path,
> co.Iface)
> }
> ```
> Implementation of the above looks like this ...
> ```
> // Create our private dbus connection structure
> dbc := newDbusObject(conn, dbusiface, dbuspath)
> err = dbc.addResponseMethod("Ping")
> if err != nil {
> fmt.Println("Failed to export method to system bus:", err)
> }
> ```
> The function does not throw any error, but an introspection of the dbus
> shows ...
> ```
> DBUS_SYSTEM_BUS_ADDRESS="unix:path=/var/run/dbusalt/system_bus_socket"
> dbus-send --system --print-reply --type=method_call
> --dest='org.openxt.ndvm.wifi' '/org/openxt/ndvm/wifi'
> org.freedesktop.DBus.Introspectable.Introspect
> method return time=1574178759.805460 sender=:1.0 -> destination=:1.1
> serial=4 reply_serial=2
> string "
> <node>
> <interface name="org.openxt.ndvm.wifi">
> <method name="Foo">
> <arg direction="out" type="s"/>
> </method>
> </interface>
> <interface name="org.freedesktop.DBus.Introspectable">
> <method name="Introspect">
> <arg name="out" direction="out" type="s"/>
> </method>
> </interface>
> </node>"
>
> ```
> Calls to the unaltered "Foo" work, "Ping" does not (of course).
>
> What am I doing wrong?
> Are there some good (current) examples in a project where they have not
> abstracted the interface so much as to be useless for learning?
> Is there a mailing list more suitable for these questions? (I could not
> find one and I hate to open issues just to ask questions.)
>
> It would be nice if someone updated the examples used under godbus to
> reflect what an actual user would have to go through to implement a full,
> usable method.
>
(Note: Also tried ...)
```
func (dbo dbusobj) addSimpleMethod(method interface{}) error {
err := dbo.Conn.Export(method, dbo.Path, dbo.Iface)
if err != nil {
return err
}
node := &introspect.Node{}
node.Name = dbo.Iface
iface := &introspect.Interface{}
iface.Name = dbo.Iface
mts := introspect.Methods(method)
iface.Methods = mts
node.Interfaces = append(node.Interfaces, *iface)
dbusXMLStr := introspect.NewIntrospectable(node)
err = dbo.Conn.Export(dbusXMLStr, dbo.Path,
"org.freedesktop.DBus.Introspectable")
if err != nil {
return err
}
return nil
}
```
Implemented as ...
```
p := ping("Ping called!")
err = dbc.addSimpleMethod(p)
```
Same result.
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