Best method to implement an abstract factory pattern

Question

Consider following code:

#include 


// =============================


class Shape{
public:
    virtual ~Shape(){};

    virtual void process         


        

Answer 1

I think the most idiomatic modern C++ method is the one you mention in passing but ignore. Return a std::unique_ptr.

It is safe, clearly expresses ownership, supports polymorphism and doesn't need much code.

class ShapeFactory {
public:
  std::unique_ptr create(){
    return std::make_unique();
  }
};

But I wouldn't want to claim it was the "best" method.

Your PimplShape in option 3 is actually very similar to a unique_ptr just less generic or tested.