Visual Basic Programming Code Examples

Visual Basic > Applications VBA Code Examples

Querying the interface of an object in a typelib (COM object)

Querying the interface of an object in a typelib (COM object)

The following code demonstrates how to iterate/enumerate all the objects in a typelib and returns the exposed interface (from the objects vTable) of these objects in an array.


'Purpose   :    Returns an array containing the exposed objects contained inside a COM object.
'Inputs    :    sFileName                   The file name of the object to return the interface of.
'Outputs   :    Returns a one based string array of object contained in a typelib.
'Notes     :    Requires "Typelib Information" (TLBINF32.DLL) to be installed.


Function TypeLibObjects(sFileName As String) As Variant
    Dim oTypeLib As Object      'TLI.TypeLibInfo
    Dim oTypeInfo As Object     'TLI.TypeInfo
    Dim asObjects() As String, lCount As Long
    
    On Error GoTo ErrFailed
    Set oTypeLib = CreateObject("TLI.TypeLibInfo")
    oTypeLib.ContainingFile = sFileName
    
    If oTypeLib.TypeInfoCount Then
        ReDim asObjects(1 To oTypeLib.TypeInfoCount)
        For Each oTypeInfo In oTypeLib.TypeInfos
            lCount = lCount + 1
            asObjects(lCount) = oTypeInfo.Name
        Next
        TypeLibObjects = asObjects
    End If
    
    Set oTypeLib = Nothing
    Set oTypeInfo = Nothing
    
    Exit Function

ErrFailed:
    Debug.Print "Error in TypeLibObjects " & Err.Description
    Debug.Assert False
End Function


'Purpose   :    Returns an array containing the interface from a COM object, i.e. iterates
'               through the entities exposed of a type library
'Inputs    :    sFileName                   The file name of the object to return the interface of.
'Outputs   :    Returns a one based string array of interface call names
'Notes     :    Requires "Typelib Information" (TLBINF32.DLL) to be installed.


Function TypeLibObjectInterface(sFileName As String, sObjectName As String) As Variant
    Dim oTypeLib As Object          'TLI.TypeLibInfo
    Dim oSearchResults As Object    'TLI.SearchResults
    Dim oThisItem As Object
    Dim asInterface() As String
    Dim lSearchData As Long
    Dim lCount As Long
    
    On Error GoTo ErrFailed
    Set oTypeLib = CreateObject("TLI.TypeLibInfo")
    oTypeLib.ContainingFile = sFileName
    
    If oTypeLib.TypeInfoCount Then
        lSearchData = oTypeLib.MakeSearchData(sObjectName)
        Set oSearchResults = oTypeLib.GetMembers(lSearchData)
        'Found required object, return interface
        ReDim asInterface(1 To oSearchResults.Count)
        For Each oThisItem In oSearchResults
            lCount = lCount + 1
            asInterface(lCount) = oThisItem.Name
        Next
        TypeLibObjectInterface = asInterface
    End If
    
    Set oTypeLib = Nothing
    Set oSearchResults = Nothing
    
    Exit Function

ErrFailed:
    Debug.Print "Error in TypeLibObjectInterface " & Err.Description
    Debug.Assert False
End Function

'Demonstration of how to return an the interface of a COM object
Sub Test()
    Dim avObjects As Variant, avInterface As Variant
    Dim lThisObject As Long, lThisItem As Long
    
    avObjects = TypeLibObjects("C:\WINDOWS\SYSTEM\MSCAL.OCX")
    For lThisObject = 1 To UBound(avObjects)
        Debug.Print "------------------------------"
        Debug.Print "Interface for object " & avObjects(lThisObject)
        avInterface = TypeLibObjectInterface("C:\WINDOWS\SYSTEM\MSCAL.OCX", CStr(avObjects(lThisObject)))
        For lThisItem = 1 To UBound(avInterface)
            Debug.Print avInterface(lThisItem)
        Next
    Next
End Sub