Re: Initializing Different ancestor constuctor based on derived input

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 19 May 2009 13:52:23 -0500

Message-ID:

<5jv515576m8uiu2n2qfvogp00kg0omoe9l@4ax.com>

On Tue, 19 May 2009 11:40:31 -0700, Electronic75
<Electronic75@discussions.microsoft.com> wrote:

Hello,
My specific problem relates to new CMFCPropertyGridProperty class(from
feature pack) depending of property type there are two different constructors
for this class
for group property->: CMFCPropertyGridProperty(strGroupName, dwData,
bIsValueList)
and for none-group
property->CMFCPropertyGridProperty(strName,varValue,lpszDescr,dwData,lpszEditMask,
                                        lpszEditTemplate,lpszValidChars)
now I have derived my own class from this complex class ->
class CPropertiesGridProp : public CMFCPropertyGridProperty
to accommodate some extra functionalities, is there a way that with a single
derived constructor and depending on input I can initialize the right
ancestor constructor? I tried this but it fails is there anyway?

CPropertiesGridProp::CPropertiesGridProp(CEntry* pxEntry)
:(pxEntry->GetPropControl() == PropCtrlGroup) ?
    CMFCPropertyGridProperty(pxEntry->m_xName)
:CMFCPropertyGridProperty(pxEntry->m_xName,
            (pxEntry->GetPropControl() == PropCtrlEditDouble)?
(_variant_t)pxEntry->m_dValue:(_variant_t)pxEntry->m_xValue,
    pxEntry->m_xComment)
, m_pxEntry(pxEntry)
{

}
I used two if else statement in form of (...)? ... : ...
the second if statement has no problem and if I remove first one it compiles
but when I compile with the first if statement it fails.

is there anyway?

No. You can't use an if-statement in the member initialization list, and
you can only use the conditional operator for individual arguments in the
ctor argument list. Even if you use the latter, you will always chain to
one and only one base class ctor based on overload resolution. You need to
create multiple ctors or, if the base class supports it, do its complex
initialization inside the ctor body; that's the place you can use an
if-statement.

--
Doug Harrison
Visual C++ MVP