is it a good practice to use nullptr as None as in python in c++

Question

I'm building a program with c++, but I'm not sure if this way is right.

class A {
  private:
    unsigned *a;

    bool checkA() {
      return a != nullptr;
    }

  public:
    A() {
      this->a = nullptr;
    }

    void setA(unsigned a) {
      this->a = new unsigned(a);
    }
}

The member variable 'a' will only be set by 'setA', however in other method, I have to check if 'a' has been set. Thus I used nullptr to check if it is set.

Is this code a good practice?

I tried to change the datatype of 'a' to int and set it to -1 to notice for an uninitialized value. However I think there would be a better way to do this.

Please give me some advices.

Answer 1

You could use std::optional<int> if you really want.

But setA itself is an anti-pattern, just set the value in the constructor, RAII is your friend, not something to actively avoid.

It is much easier to reason about the code if a is always present than A being stateful with sometimes having a, sometimes not.