[Gambas-user] D-Bus method with a complex data type triggers an error

[Hans Lehmann]

Am 13.03.2018 um 16:58 schrieb Benoît Minisini:
> Struct are not used by gb.dbus. 

This is understandable at http://gambaswiki.org/wiki/doc/dbus#t10. I 
didn't use such a structure on the D-Bus server either.

> Compound values are returned as an array of variants. 

That's how I realized it with three classes.
I oriented myself on the source code of the component gb.dbus.trayicon.

FMain.class:
------------------

Public hDBusObject As TService

Public Sub Form_Open()

   hDBusObject = New TService

   FMain.Resizable = False
   FMain.Caption = ("The data server is activated")

   DBus.Unique = True

   Try DBus.Session.Register(hDBusObject, "/TService")
   If Error Then
      Message.Error("An instance of " & Application.Name & " already 
exists.")
      FMain.Close()
   Endif

End

Public Sub Form_Close()

   If DBus.IsRegistered(hDBusObject) Then 
DBus.Session.Unregister(hDBusObject)
   FMain.Close()

End


TService.class:
----------------------

Inherits DBusObject
Create Static

Public Function GetTemperature(Trigger As String) As RValue

   Dim hItem As RValue
   Dim s1, s2, s3, s4 As String
   Dim i1, i2, i3, i4 As Integer
   Dim f1 As Float
   Dim aTime As Variant[]
   Dim cTemperature As Collection

   i1 = Day(Now())
   s1 = Format(Now(), "mmmm")
   i2 = Year(Now())

   i3 = Hour(Now())
   i4 = Minute(Now())
   s2 = "UTC"
   aTime = [i3, i4, s2]

' The temperature value is read out in real operation from an RS232-AD 
converter
   f1 = 22.4 '
   Select Case Trigger
     Case "C"
       s3 = "°"
       s4 = "C"
     Case "K"
       f1 = f1 + 273.15
       s3 = ""
       s4 = "K"
     Case "F"
       f1 = (9 / 5) * f1 + 32
       s3 = "°"
       s4 = "F"
   End Select

   cTemperature["T"] = f1  ' Temperature
   cTemperature["L"] = s3  ' Label
   cTemperature["S"] = s4  ' Scale

   hItem = New RValue
   hItem.Value = [i1, s1, i2, aTime, cTemperature] ' <<-- Compound 
values are returned as an array of variants.

   Return hItem

End

RValue.class:
-------------------
' This class RValue (stands for ReturnValue) is needed to define the 
complex return type with the signature' isiava{sv}:

Export
Inherits DBusVariant

Public Const Signature As String = "isiava{sv}"

---

The error occurs at the client in dbusc.class:

Public hDBusProxy As DBusProxy

Public Struct StructVariant
   String1 As String
   Integer1 As String
   String2 As String
   Array As Variant[]
   Collection As Collection
End Struct

Public structS As New StructVariant

Public Sub Form_Open()

Dim sMessage As String

   DBus.Debug = True
   FMain.Resizable = False

   If Not DBus.Session.Applications.Exist("org.gambas.dbuss") Then
      sMessage = ("There is no suitable data server on the session bus!")
      sMessage &= "<center><font color='red'>"
      sMessage &= ("The program is terminated.")
      sMessage &= "</font></center>"
      Message.Warning(sMessage)
      FMain.Close()
   Else
     hDBusProxy = DBus["org.gambas.dbuss"]["/TService"]
     GetData()
   Endif
End

Private Sub GetData()

   structS = hDBusProxy.GetTemperature(tboxScale.Text) --> ERROR: 
org.freedesktop.DBus.Error.Failed: Zero object?

End

Public Sub btnGetData_Click()
   GetData()
End

Public Sub Form_Close()
   FMain.Close()
End

The question remains as to why this error occurs?

With kind regards

Hans