Question about CreateObject

[WesWesthaver]

I just created my first PB based COM server and tried to use it with vbScript. I assumed that the syntax should be:

Set Obj = CreateObject("EPSON_822.Projector")

Since my CLASS=EPSON_822 and my INTERFACE=Projector. However, the object fails to be created.

But when I use only the Class name without the interface name it works. ie:

Set Obj = CreateObject("EPSON_822")

I've never seen this before and I don't understand it. The following are examples of objects that I use frequently and they all require the CLASS.INTERFACE syntax.

Set GUIDGEN = CreateObject("GUIDGenerator.GUIDGEN")
Set Connection = CreateObject("ADODB.Connection")
Set Recordset = CreateObject("ADODB.Recordset")
Set fso = CreateObject("Scripting.FileSystemObject")
Set objMailSender = CreateObject("Persits.MailSender")

Can anyone tell me what I'm missing? Obviously there's a large gap in my understanding.

-Wes

[Dominic Mitchell]

But when I use only the Class name without the interface name it works. ie:

Can anyone tell me what I'm missing? Obviously there's a large gap in my understanding.

Let me give you a hint.
Did you assign a programmatic id to the coclass?

[WesWesthaver]

Let me give you a hint.
Did you assign a programmatic id to the coclass?

Well, I'm so new to this stuff that I'm not sure what you mean. Here's what my code looks like:

'------------------------------------------------------------------------------
' Compiler meta statements
'------------------------------------------------------------------------------
'
#Compile Dll
#Dim All
#Com Name "EPSON_822", 1.00
#Com Guid Guid$("{96743A31-E8AB-48F4-919C-8A0B9BC25D5D}")
#Com TLib On
 
'------------------------------------------------------------------------------
' Projector class
'   Provides the basic control interface for a generic data projector
'------------------------------------------------------------------------------
'
Class EPSON_822 Guid$("{B4E61282-8F67-4AE9-B3F1-79771CB93D2B}") As Com
  '----------------------------------------------------------------------------
  ' Instance variables
  '
  Instance strIP        As String
  Instance lngPort      As Long
  '----------------------------------------------------------------------------
  ' Class interface
  '
  Interface Projector Guid$("{698E3BCA-3ADB-4918-A9B3-461044C5754F}")
    '--------------------------------------------------------------------------
    ' Inherit from idispatch base class
    '
    Inherit IDispatch
 
    '--------------------------------------------------------------------------
    ' Properties
    '--------------------------------------------------------------------------
    Property Get IP <30> () As String
      Property = UCode$(strIP)
    End Property
    Property Set IP <30> (ByVal strNewValue As String)
      strIP = ACode$(strNewValue)
    End Property
    '--------------------------------------------------------------------------
    Property Get Port <40> () As Long
      Property = lngPort
    End Property
    Property Set Port <40> (ByVal lngNewValue As Long)
      lngPort = lngNewValue
    End Property
    '--------------------------------------------------------------------------
    Property Get Power <50> () As Byte
      Property = me.GetPower
    End Property
    Property Set Power <50> (ByVal bytNewValue As Byte)
      me.SetPower(bytNewValue)
    End Property
    '--------------------------------------------------------------------------
    Property Get Volume <60> () As Byte
      Property = me.GetVolume
    End Property
    Property Set Volume <60> (ByVal bytNewValue As Byte)
      me.SetVolume(bytNewValue)
    End Property
    '--------------------------------------------------------------------------
    Property Get VideoSource <70> () As Byte
      Property = me.GetVideoSource
    End Property
    Property Set VideoSource <70> (ByVal bytNewValue As Byte)
      me.SetVideoSource(bytNewValue)
    End Property
    '--------------------------------------------------------------------------
    Property Get LampHours <80> () As Integer
      Property = me.GetLampHours
    End Property
 
    '--------------------------------------------------------------------------
    ' Methods
    '--------------------------------------------------------------------------
    '
    Method On <10> ()
      me.SetPower(1)
    End Method
    Method Off <20> ()
      me.SetPower(0)
    End Method
 
  End Interface
 
  '----------------------------------------------------------------------------
  ' Private class methods
  '----------------------------------------------------------------------------
  '
  Class Method Create()
    ' Initialize IP and Port vars.
    '
    strIP = "0.0.0.0"
    lngPort = 3629
  End Method
  Class Method Destroy()
    ' Do nothing.
  End Method
  '----------------------------------------------------------------------------
  Class Method GetPower() As Byte
    Local strResponse As String
    strResponse = me.ProjectorCommand("PWR?" + $Cr, 5)
    Method = Val(me.GetValueFromNVP(strResponse, "PWR"))
  End Method
  Class Method SetPower(bytNewValue As Byte)
    Select Case bytNewValue
      Case 0
        me.ProjectorCommand("PWR OFF" + $Cr, 60)
      Case Else
        me.ProjectorCommand("PWR ON"  + $Cr, 60)
    End Select
  End Method
  '----------------------------------------------------------------------------
  Class Method GetVolume() As Integer
    Local strResponse As String
    strResponse = me.ProjectorCommand("VOL?" + $Cr, 5)
    Method = Val(me.GetValueFromNVP(strResponse, "VOL"))
  End Method
  Class Method SetVolume(bytNewValue As Byte)
    me.ProjectorCommand("VOL" + Str$(bytNewValue) + $Cr, 5)
  End Method
  '----------------------------------------------------------------------------
  Class Method GetVideoSource() As Integer
    Local strResponse As String
    strResponse = me.ProjectorCommand("SOURCE?" + $Cr, 5)
    Method = Val(me.GetValueFromNVP(strResponse, "SOURCE"))
  End Method
  Class Method SetVideoSource(bytNewValue As Byte)
    me.ProjectorCommand("SOURCE" + Str$(bytNewValue) + $Cr, 5)
  End Method
  '----------------------------------------------------------------------------
  Class Method GetLampHours() As Integer
    Local strResponse As String
    strResponse = me.ProjectorCommand("LAMP?" + $Cr, 5)
    Method = Val(me.GetValueFromNVP(strResponse, "LAMP"))
  End Method
 
  '----------------------------------------------------------------------------
  ' TCP/IP communication methods
  '----------------------------------------------------------------------------
  '
  Class Method ProjectorConnect(lngTimeout As Long) As Long
 
    ' Code removed because of NDA
 
  End Method
  '----------------------------------------------------------------------------
  Class Method ProjectorDisconnect(lngFileNum As Long)
    Tcp Close lngFileNum
  End Method
  '----------------------------------------------------------------------------
  Class Method ProjectorCommand(strCommand As String, lngTimeout As Long) As String
    Local lngFileNum As Long
    lngFileNum = me.ProjectorConnect(lngTimeout)
    Me.TX(lngFileNum, strCommand)
    Method = me.RX(lngFileNum,":")
    me.ProjectorDisconnect(lngFileNum)
  End Method
  '----------------------------------------------------------------------------
  Class Method TX(lngFileNum As Long, strCommand As String)
    Tcp Send lngFileNum, strCommand
  End Method
  '----------------------------------------------------------------------------
  Class Method RX(lngFileNum As Long, strEOT As String) As String
    Local strTemp    As String
    Local strBuffer  As String
    strTemp = ""
    strBuffer = ""
    Do
      Tcp Recv lngFileNum, 1024, strBuffer
      strTemp = strTemp + strBuffer
      If IsTrue Err Then
        MsgBox "RX: Error=" + Str$(Err),, "EPSON_822.DLL"
        ErrClear
        Exit Do
      End If
      If strBuffer = "" Then
        MsgBox "RX: buffer empty",, "EPSON_822.DLL"
        Exit Do
      End If
      If strEOT <> "" Then
        If InStr(strTemp, strEOT) Then
          'msgbox "RX: EOT",, "EPSON_822.DLL"
          Exit Do
        End If
      End If
    Loop
    Method = strTemp
  End Method
  '----------------------------------------------------------------------------
  Class Method GetValueFromNVP(strInput As String, strFind As String) As String
    Local intIndex   As Integer
    Local strArray() As String
    Local strName    As String
    Local strValue   As String
    Dim strArray(1 To ParseCount(strInput, $Cr))
    Parse strInput, strArray(), $Cr
 
    ' Check for error in projector response
    '
    For intIndex = 1 To UBound(strArray)
      If Left$(strArray(intIndex), 3) = "ERR" Then
        MsgBox "Projector returned an ERR",, "EPSON_822.DLL"
        Method = ""
        Exit Method
      End If
    Next intIndex
    ' Find the specified name and return its value
    '
    For intIndex = 1 To UBound(strArray)
      If Left$(strArray(intIndex), Len(strFind)) = strFind Then
        If InStr(strArray(intIndex), "=") Then
          strName = Extract$(strArray(intIndex),"=")
          strValue = Remain$(strArray(intIndex),"=")
          Method = strValue
          Exit For
        End If
      End If
    Next intIndex
  End Method
End Class

And here's the resulting COM Browser info:

' Generated by: PowerBASIC COM Browser v.2.00.0058
' DateTime    : 2/5/2009 at 2:42 PM
' ------------------------------------------------
' Library Name: EPSON_822
' Library File: F:\Projector Control Project\COM\EPSON_822.DLL
' Description : COM Library
' GUID : {96743A31-E8AB-48F4-919C-8A0B9BC25D5D}
' LCID : 0
' Version : 1.0
' Class Indentifiers
$CLSID_EPSON_822_EPSON_822 = GUID$("{B4E61282-8F67-4AE9-B3F1-79771CB93D2B}")
' Interface Indentifiers
$IID_EPSON_822_PROJECTOR = GUID$("{698E3BCA-3ADB-4918-A9B3-461044C5754F}")
' Interface Name  : PROJECTOR
' Description     : PROJECTOR is a dual interface with IDispatch.
' ClassID         : $CLSID_EPSON_822_EPSON_822
Interface PROJECTOR $IID_EPSON_822_PROJECTOR 
    Inherit IDispatch
    Property Get IP <30> () As String
    Property Set IP <30> (ByVal Rhs As String)
    Property Get PORT <40> () As Long
    Property Set PORT <40> (ByVal Rhs As Long)
    Property Get POWER <50> () As Byte
    Property Set POWER <50> (ByVal Rhs As Byte)
    Property Get VOLUME <60> () As Byte
    Property Set VOLUME <60> (ByVal Rhs As Byte)
    Property Get VIDEOSOURCE <70> () As Byte
    Property Set VIDEOSOURCE <70> (ByVal Rhs As Byte)
    Property Get LAMPHOURS <80> () As Integer
    Method ON <10> ()
    Method OFF <20> ()
End Interface

[Fred Harris]

Set Obj = CreateObject("EPSON_822.Projector")

I don't see where you are getting the .Projector part from Wes. It looks to me like the ProgID doesn't have that part.

Also, I don't believe IDispatch based objects can have more than one interface, which is by default the 'default interface'. So doing late binding with just the ProgID will give you the first and only interface in the class.

[Dominic Mitchell]

You are probably thinking of a programmatic identifier(ProgID) in terms of the unofficial naming convention

<program>.<component>.<version>

PowerBASIC just simply uses the class name as the programmatic id. Not a good idea
in my opinion.
You have no control over this and a slew of other things unless you decide to tweak the type libary
file(*.tlb).

When you register your server with regsvr32.exe, PowerBASIC creates the following entries in the
Registry:

HKEY_CLASSES_ROOT\CLSID\{B4E61282-8F67-4AE9-B3F1-79771CB93D2B}\ProgID\EPSON_822
HKEY_CLASSES_ROOT\TypeLib\{96743A31-E8AB-48F4-919C-8A0B9BC25D5D}\1.0\...

And that is why CreateObject("EPSON_822") worked.

[Bob Zale]

Hi Wes,

I'm afraid Dominic isn't entirely correct on this one. Most languages, including PowerBASIC and VB, use a ProgID to identify a CLASS. A ProgID is a relatively short alphanumeric identifier which specifies a particular CLASS on your computer. In effect, it's a shorter, friendlier version of the Class ID (CLSID) which uniquely identifies the class globally. It's expected that a ProgID might be duplicated on computers other than yours, as the nature of the identifier is much simpler.

Note that a ProgID does not identify a CLASS/INTERFACE combination, but rather, just a CLASS, including all of its interfaces. When you create an object variable in PowerBASIC, the ProgID specifies the CLASS, and the variable definition specifies the interface you wish to use. You combine the two items when you instantiate an object. Most languages follow conventions of that sort.

Since the ProgID specifies only the CLASS, we've chosen to use the CLASS name as the ProgID. That makes it short, descriptive, and very easy for you to remember. If you'd like to make it more complex, and therefore more unique, you only need to change the class name to something much longer, more complicated, and therefore less likely to clash. The choice is entirely in your hands to do with as you wish. If you are more comfortable using a class/interface combination, there's nothing to prevent you from just extending/expanding the class name to suit your whim-of-the-day! {smile}

Best regards,

Bob Zale
PowerBASIC Inc.

[WesWesthaver]

Wow, I guess I have to plead mea-culpa for my ignorance. In trying to understand what I have been seeing all these years I fashioned a bizzare explanation in my own mind that was entirely bogus.

It never occured to me that the naming convention I've observed all these years like:

"ADODB.Connection"
"ADODB.Recordset"
"Scripting.FileSystemObject"

was just that... a naming convention! Somehow I assumed that it was some sort of concatenation of the Class name and the Interface name that was created at compile time.

Now it appears that it's just a naming convention applied to the ProgID.

Sometimes I think VisualBasic really is damaging to your abilities as a programer. VB let me accomplish my goals but kept me confused about its inner workings. I guess this is what happens when you've worked with VisualBasic for too many years.

Anyway, if I wanted to adopt this naming convention, I would do something like this?:

#COM NAME "ProgramName.ObjectName", 1.00

or in my particular case

#COM NAME "ProjectorNET.EPSON_822", 1.00

-Wes

[WesWesthaver]

PS. I found this in an MSDN article:

The format of <ProgID> is <Program>.<Component>.<Version>, separated by periods and with no spaces. The ProgID must comply with the following requirements:

• Have no more than 39 characters.
• Contain no punctuation (including underscores) except one or more periods.
• Not start with a digit.
• Be different from the class name of any OLE 1 application, including the OLE 1 version of the same application, if there is one.

So it appears that the use of the underscore in my current COM object ProgID ("EPSON_822") is illegal (even though it seems to work just fine.) Hmmm... so much to take in.

[Dominic Mitchell]

Anyway, if I wanted to adopt this naming convention, I would do something like this?:

#COM NAME "ProgramName.ObjectName", 1.00

or in my particular case

#COM NAME "ProjectorNET.EPSON_822", 1.00

No, that is not going to give you the programmatic ID. Because PowerBASIC uses the class name for
the programmatic ID, it can never produce one that looks like this

<Program>.<Component>.<Version>

for the simple reason that, for example, EPSON_822.Projector is not a legal name in PB.

In my opinion, PowerBASIC needs a metastatement that allows the programmer to define the programmatic ID.
Something like #COM PROGID with the option to set both version dependent and version independent forms.

At present, to produce that type of programmatic ID, you will need to write your own DllRegisterServer function.

PS. I found this in an MSDN article:
...

Ignore the part that deals with length and underscores.

[Bob Zale]

Wes, what Dominic failed to tell you was the difference between the two names. The #COM NAME metastatement specifies the Application ID (AppID) or the Library ID (LibID), which is the (optional) name of the entire component or server. A ProgID is the name of a single CLASS. Of course, there can optionally be many classes contained within a single COM component (server).

I see that he also extended permission {smile} to ignore certain COM rules regarding naming conventions. Even so, PowerBASIC recommends that you follow those rules for best results.

Best regards,

Bob Zale
PowerBASIC Inc.

[WesWesthaver]

Because PowerBASIC uses the class name for the programmatic ID, it can never produce one that looks like this

<Program>.<Component>.<Version>

for the simple reason that, for example, EPSON_822.Projector is not a legal name in PB.

Dominic, If you're right, that seems like a really odd design decision to build the compiler in such a way that it won't allow you to name your COM objects in the format that virtually everyone in the industry uses??? That's kind of disappointing. How often does PB get updated? Maybe this can be addressed in the near future? Along with Enums and property attributes....

-Wes

[Larry Charlton]

Two thoughts:
#COMBASE "BaseName"
#COMBASE DLL
#COMBASE NOTHING

Is that three? *smack*

[Michael Mattias]

Sometimes I think VisualBasic really is damaging to your abilities as a programer. VB let me accomplish my goals but kept me confused about its inner workings. I guess this is what happens when you've worked with VisualBasic for too many years.

Duh. Ya Think?