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POPassing a VBA class that implements an ATL interface, to an ATL method
 

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  1. POPassing a VBA class that implements an ATL interface, to an ATL method
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    <p><strong>Edit :</strong></p> <p>I have an ATL simple object MyATLObject, having only one method :</p> <pre><code>STDMETHODIMP CMyATLObject::EVAL( DOUBLE* x, long AddressOfFunc ) { *x = toto&lt;FCTPTR&gt;(*((FCTPTR) AddressOfFunc)) ; return S_OK; } </code></pre> <p>where toto is a template function defined by</p> <pre><code>#pragma once template&lt;typename F&gt; double toto( F f ) { return f(0.0) ; } </code></pre> <p>and where FCTPTR is defined as</p> <p>typedef double (__stdcall * FCTPTR)( double );</p> <p>My ATL method consume double x for storing the result of toto, and long AddressOfFunc which is the AddressOf of a VBA function.</p> <p>This passing VBA function to ATL methods by Address. it is quite awful. How would it be able to do the same - passing VBA functions - to ATL method otherwise, for instance by defining an interface on the ATL side ?</p> <p>Thank you very much.</p> <p>//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////</p> <p><strong>First version of my question :</strong></p> <p>I am actually doing the following : creating an ATL/COM project, adding a "simple ATL object" called MyATLObject to it with :</p> <p>1) in the idl file :</p> <pre><code>interface IMyATLObject : IDispatch{ [id(1), helpstring("method EVAL")] HRESULT EVAL(DOUBLE* x, long AddressOfFunc) ; }; </code></pre> <p>2 in the MyATLObject.h file :</p> <p>an</p> <pre><code>#include "MyStupidEvaluator.h" </code></pre> <p>and a</p> <pre><code>typedef double (__stdcall * FCTPTR)( double ); </code></pre> <p>outside the class, and in the class </p> <pre><code>public: STDMETHOD(EVAL)(DOUBLE* x, long AddressOfFunc) ; </code></pre> <p>and finally in the MyATLObject.cpp file :</p> <pre><code>STDMETHODIMP CMyATLObject::EVAL( DOUBLE* x, long AddressOfFunc ) { *x = toto&lt;FCTPTR&gt;(*((FCTPTR) AddressOfFunc)) ; return S_OK; } </code></pre> <p>MyStupidEvaluator.h contains :</p> <pre><code>#pragma once template&lt;typename F&gt; double toto( F f ) { return f(0.0) ; } </code></pre> <p>This is just a template function that returns the value at zero of any function object, that is a typename (or a class) admitting a () operator.</p> <p>Now, this gives to me, after compilation, a dll.</p> <p>That's all for the c++ part. Now, I'm referencing this dll in VBA and in VBA :</p> <p>a) I define a function</p> <pre><code>Public Function F(ByVal x As Double) As Double F = x * x - 2 * x + 1 End Function </code></pre> <p>b) and a sub</p> <pre><code> Public Sub Draft1() Dim ENGINE As MyTestProjectLib.MyATLObject Set ENGINE = New MyTestProjectLib.MyATLObject Dim x As Double x = 0# Call ENGINE.EVAL(x, AddressOf F) Sheets("Test1").Range("Value_at_0").Offset(0, 0).Value = x End Sub </code></pre> <p>c) Executing this sub will give to me, in the range V"alue_at_0" (just a cell here) of the sheet "Test1" the value at 0.0 of the function F.</p> <p>I'm always working like this : the toto template function is trivial here (evaluation at 0.0) but in general it could be a numerical integration routine, or a root finding routine for which c++ is needed for quickness ; I'm alwas passing VBA functions through their addresses, thanks to the AddressOf VBA keyword : this gives me a long that I pass to my ATL method EVAL, I convert this long in function pointer (FCTPTR) p, and I apply my routine "toto" to *p, which gives a double to me, that I pass back to my ATL method.</p> <p>That's cool, everything works, but... I find this awful !!! And really inelegant. That's why I would like to do the following :</p> <p>design "somehow" an interface on the ATL side, a</p> <pre><code>interface IMyFunction : IDispatch </code></pre> <p>that would be implemented (through VBA's implements) in VBA by a VBA class VBAClass1, and pass an instance of that VBA class to a new version of my former VBA method for performing the evaluation at 0.0.</p> <p>My problem is : I'm not an expert at all in ATL, nor in interface creating : I've succeeded in doing real stupid/trivial things in interface creating, ok, but I really don't see how to design the interface doing what I want to do, that is :</p> <p>an interface in ATL (which will by definition have only methods, by ATL construction !) that would have "something" playing the role of a member of a class, member keeping track of a VBA function still to be passed to him through an ATL method.</p> <p>Any help would be greatly appreciated, folks.</p> <p>It's my first time here, so sorry per advance if the message is not in the perfect/optimal form.</p> <p>Thank you in advance.</p> <p>Raph</p>
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