C++: Initialize a member pointer to null?

Question

I have a class that looks like:

class Foo { public:     Foo();     virtual ~Foo();  private:     Odp* bar; }; 

I wish to initialize bar to NULL. Is this the best way to do it?

Foo::Foo() : bar(NULL) { } 

Also, is it necessary that the destructor is virtual? (If that is true, then must the constructor be virtual as well?)

Answer 1

I wish to initialize bar to NULL. Is this the best way to do it?

It is the correct way. So, yes.

Also, is it necessary that the destructor is virtual?

No. The destructor only needs to be virtual if you will be inheriting from the Foo class and will be using a Foo pointer to delete those derived classes (although as a general rule of thumb, it should be virtual if there are any other virtual members).

(If that is true, then must the constructor be virtual as well?)

No. Constructors neither need to be virtual, nor can they.

Answer 2

1. Yes, the initializer list is best.

2. Maybe. The destructor should be virtual if you intend to have any other virtual functions in the class, or if you intend the class to be inherited from (although usually those things go together).

3. No. It's not possible to have a virtual constructor in C++. (what would such a thing even mean?)

The nature of your question suggests to me that you don't really understand what the virtual keyword does, or what is is for, and you are just copying something you saw elsewhere or in a tutorial. It's best to understand the purpose of all of the code you're writing. Here might be a place to start: http://www.parashift.com/c++-faq-lite/virtual-functions.html