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| Title | Use the TypeLib routine Invokehook to find a control's name and invoke a routine |
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| Description | This example shows how to use the TypeLib routine InvokeHook to find a control's name and invoke a routine in Visual Basic 6. It uses the InvokeHook method with the INVOKE_PROPERTYGET command to invoke the control's Name property. It uses the INVOKE_FUNC command to invoke the routine. |
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| Keywords | TypeLib, InvokeHook, get name |
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| Categories | Software Engineering, Controls |
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Thanks to Sergio Perciballi.
The program needs a reference to typelib information (tLbinf32.dll). MSDN has tLbinf32.dll documentation in addons area http://msdn.microsoft.com/vbasic/downloads/addon.asp and http://msdn.microsoft.com/vbasic/downloads/download.asp?ID=094. Sergio says "If you can understand this documentation then you must be a COM programmer!"
The hook subroutine calls InvokeHook, passing it a control, the name of the property to invoke (Name), and the INVOKE_PROPERTY command.
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Private m_TLInf As TypeLibInfo
Sub hook()
Dim ret As Variant
'The Invoke members of the TLIApplication object
'allow you to easily use IDispatch::Invoke directly
' from VB code
'This has similar functionality to the VB6 callbyname
' function
'I left out The ReverseArg();ret receives the property
' value
ret = tli.InvokeHook(Me.TxtThisIsTheName, "Name", _
INVOKE_PROPERTYGET)
MsgBox "The name of this textbox is '" & ret & "'"
End Sub
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Subroutine hook2 invokes the form's foo subroutine. It calls InvokeHook passing it the name of the object (the form), the name of the method to invoke (foo), the INVOKE_FUNC command, and an array of arguments for the foo method.
The foo method displays its arguments.
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Sub hook2()
'call a function of form1 object
'foo(integer,integer array)
'Function call takes 2 arguments
Dim tli As TLIApplication
Set tli = New TLIApplication
Dim arg() As Variant, iarr() As Integer
Dim i As Integer
Dim vt As Integer
ReDim args(1): ReDim iarr(1)
iarr(0) = 77: iarr(1) = 12345
'arguments for function are in reverse order: Order
' that IDispatch::Invoke wants them
'pointer to the integer array put in arg array which
' ia a variant array
args(0) = VarPtrArray(iarr)
'In order to support ByRef parameters with
' InvokeHookArray,
'you'll have to modify the Variants in the argument
' list by assigning a Long pointer value to the
' Variant, then using the CopyMemory API to modify the
' vt (VarType) field in the underlying Variant
' structure to be the VarType of the argument combined
' with the VT_BYREF bit.
vt = VT_BYREF Or VT_ARRAY Or VT_I2
CopyMemory args(0), vt, 2
args(1) = VarPtr(i)
vt = VT_BYREF Or VT_I2
CopyMemory args(1), vt, 2
tli.InvokeHookArray Form1, "Foo", INVOKE_FUNC, args
Set tli = Nothing
End Sub
Sub foo(i As Integer, iarray() As Integer)
Dim x As Integer
MsgBox "In Foo subroutine: i= " & i
''MsgBox "iarray(0) " & iarray(0)
MsgBox "iarray count= " & UBound(iarray) + 1
'assume Lbound=0
For x = 0 To UBound(iarray) '- 1
MsgBox "iarray( " & x & ")= " & iarray(x)
Next x
End Sub
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