Regarding Virtual Constructor

ramesh

Why do we have a virtual destructor and why cant we have a virtual
constructor?

May 22 '06 #1

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Sumit Rajan

"ramesh" <ra**********@yahoo.co.in> wrote in message
news:11**********************@38g2000cwa.googlegro ups.com...

Why do we have a virtual destructor and why cant we have a virtual
constructor?

See:
http://www.parashift.com/c++-faq-lit....html#faq-20.7
http://www.parashift.com/c++-faq-lit....html#faq-20.8

Regards,
Sumit.

May 22 '06 #2

Victor Bazarov

ramesh wrote:

Why do we have a virtual destructor and why cant we have a virtual
constructor?

Until the object is fully constructed (and its final type known), how
would you decide which constructor function to invoke to construct it?

There is a "virtual constructor" idiom, look it up, but it's not a C++
concept, although it's used in C++.

V
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Please remove capital 'A's when replying by e-mail
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May 22 '06 #3

Sunil Varma

ramesh wrote:

Why do we have a virtual destructor and why cant we have a virtual
constructor?

An object is constructed on calling the constructor.
Virtual functions are associated to objects.
A constructor is called before the object is constructed.
So you cannot associate a constructor after the object is created.

May 22 '06 #4

Rolf Magnus

Victor Bazarov wrote:

ramesh wrote:
Why do we have a virtual destructor and why cant we have a virtual
constructor?

Until the object is fully constructed (and its final type known), how
would you decide which constructor function to invoke to construct it?

Well, the final type is always known at compile time when constructing an
object. That's why a virtual constructor makes no sense.

May 22 '06 #5

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