Jump to content
  • Advertisement
Sign in to follow this  
Nene

Dynamic_cast in constructor. Please

This topic is 3601 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi everyone, I have a problem with the following dynamic_cast (it returns 0): template<class T> class Base { public: Base(){ T* t = dynamic_cast<T*>(this); } virtual ~Base(){} }; class Derived : public Base<Derived>{ public: Derived():Base(){} void g(){} }; int main() { Derived d; } Any suggestion? Thanks a lot!!! :)

Share this post


Link to post
Share on other sites
Advertisement
During Base::Base(), derived classes aren't constructed yet. It would be unsafe to access their members or member functions.

Consider:

template<class T>
class Base
{
Base()
{
T *self = dynamic_cast<T*>(this);

self->frobnicate();
}
}

class Derived : public Base<Derived>
{
void frobnicate()
{
// manipulate member.
}

std::string member;
};


If the dynamic_cast returned a pointer, and we call frobnicate on it, the code would probably crash at run time. That is a best case scenario - it could also silently corrupt unrelated memory, creating a debugging nightmare.

Share this post


Link to post
Share on other sites
Also, CRTP.

Note that template specialization is resolved at compile-time. But it is still not safe to use Derived's functions in constructor.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!