Re: [Boost-users] [SmartPtr] enable_shared_from_raw

Subject: Re: [Boost-users] [SmartPtr] enable_shared_from_raw
From: Bjorn Reese (breese_at_[hidden])
Date: 2014-07-27 09:03:06

On 07/24/2014 06:53 AM, Gavin Lambert wrote:

> 1. shared_from_this can't be used from the constructor (requiring
> factory-method-init shenanigans); reportedly

If you are using C++11, then your factory can be made generic by using
perfect forwarding:

   class my_class : enable_shared_from_this<my_class>
   {
   public:
     template <typename... Types>
     static std::shared_ptr<my_class> create(Types&&... args)
     {
       std::shared_ptr<my_class> self
         (new my_class{std::forward<Types>(args)...});
       self->init(std::forward<Types>(args)...);
       return self;
     }
   private:
     my_class();
     init();
   };

In the above, there must be an init() function for each constructor.

> And it should be possible to obtain that weak_ptr before any shared_ptr
> exists, and "fix" it later to point at the real shared_ptr, especially
> if it is known that the weak_ptr will never actually be used until that
> real shared_ptr exists.

This sounds a bit risky if the last assumption does not hold.