Re: Reallocating arrays of classes

19 Oct 2006 16:06:31 -0700
Nigel in the aerospace buisness wrote:

How do I resize an array of classes which have been allocated using new in
Visual c++ 6
class MyClass

int main()
   MyClass *pMyClass = new MyClass[5];
  pMyClass = (MyClass*)realloc(pMyClass,7 * sizeof MyClass);
   delete [] pMyClass;

This doesn't work

You can't. The only way to modify an array's size is to create it.
An array has a constant size and thats guarenteed.
And you don't need new / delete to prove that.

int main()
   MyClass arrayfive[5];
   MyClass arrayten[10];
   for(size_t i = 0; i < 5 ; ++i)
      arrayten[i] = arrayfive[i];

Have you looked at std::vector? Its an array on steroids, or rather -
to be politically correct, on vitamins.

#include <vector>

int main
   std::vector< MyClass > myvec(10); // container now has 10 elements,
all def constructed
   MyClass instance;
   myvec.pushback( instance ); // 11
   myvec.pushback( instance ); // 12

   return 0;
} // 12 elements and one container destroyed automatically

And if your class had a parametized ctor, say an integer, you could
create 100 MyClass dynamic elements all with a member integer set to 99
with one line:

std::vector< MyClass > vec(100, 99); // automatically deallocated

Can you say priceless?

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