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From: Mike Austin <m.austin@ix.netcom.com>
Subject: Can't convert function pointers where arguments are a subclass?
Date: 2000/03/08
Message-ID: <38C60A5E.ED4829BF@ix.netcom.com>#1/1
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I can see that one way would let RenderMessage act upon a Message and
cause problems, but what about the other way around?  An base object
pointer is safe to operate on a derived class.  As an example:

struct Message { };
struct RenderMsg : Message { };

class Visual {
 public:
    virtual void Render1( RenderMsg *msg ) { }
    virtual void Render2( Message *msg ) { }
};

void (Visual::*method1)( Message* ) = &Visual::Render1;
void (Visual::*method2)( RenderMsg* ) = &Visual::Render2;

Neither of the last two lines compile.


Mike

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