CODEWITHSUNDEEP
c++pointers
Coolboy
Coolboy

Reputation: 51

Casting is not a pointer type when downcasting

I have a base class:

class Base{
   public:
      Base();
      virtual ~Base();
      .....
}

class Derived2: public Base{
    public:
       Derived2();
       ...
}

and in my main, i tried to dynamic cast boost::shared_ptr from base to derived2:

  testFunction(boost:shared_ptr<Base> base){
     Derived2*  derived2 = dynamic_cast<Derived2*>(base);
}

Upvotes: 0

Views: 91

Answers (2)

eerorika
eerorika

Reputation: 238401

The operand of a dynamic_cast is not a pointer type

how can i fix it?

By not using a non-pointer type as operand of dynamic_cast. In other words, by using a pointer type as the operand.

You can get a pointer from a shared pointer using get member function.

Be careful to not let this bare pointer leak to outside the scope of the function. You can trust on its validity only as long as the argument base points to the object. Also don't attempt to take ownership of that bare pointer, since its ownership is already shared.

P.S. std::shared_ptr has been in the standard library since C++11.

P.P.S. dynamic_cast is a code smell.

Upvotes: 0

David G
David G

Reputation: 96835

Boost has dynamic_pointer_cast:

boost::shared_ptr<Derived2> derived2 = boost::dynamic_pointer_cast<Derived2>(base);

Upvotes: 1

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