Re: Instantiation of Base Class.

From:
Chris Uzdavinis <cuzdav@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Mon, 28 Jul 2008 23:28:19 CST
Message-ID:
<6ae4f1d1-e75a-4e1d-be9b-fe2dfd082da9@k13g2000hse.googlegroups.com>
On Jul 28, 7:33 pm, AY <techreposit...@gmail.com> wrote:

I'm quiet sure the member data ' testData ' can't be initialized by
Msg::TradeMsg class nor by Msg::OrderMsg class. But wanted to double
check if there is any way, we can instantiate Msg::testData from
TradeMsg && OrderMsg, preserving the class Msg declaration. Sample
code follows:

// Lets preserve the declaration of class Msg as is..
class Msg{
    public:
        int testData;
    public:
        Msg();
        class TradeMsg;
        class OrderMsg;
        ~Msg();

};

class Msg::TradeMsg{
    public:
        TradeMsg(){
            // Can we instantiate the Msg datamember like
this ?
            testData = 5;
        }

        ~TradeMsg(){

        }

};


No, there is no way to do that as you are showing. For that matter,
the type TradeMsg and OrderMsg are nested types inside Msg, but they
are not descendent types from Msg, and (presumably) do not contain a
Msg data member. Unless you explicitly create it (via inheritance or
aggregation) there is no instance of Msg at all when you instantiate
an OrderMsg or TradeMsg.

--
Chris

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