[boost] Re: [serialization] load_construct proposal

From: Robert Ramey (ramey_at_[hidden])
Date: 2003-10-12 22:50:17

>Your list omits the main motivation and benefit, ie support for 
>non-intrusive serialisation of standard containers. I would argue that the 
>serialisation fails to fulfill its design objectives without it. The 
>alternatives involve either providing a default constructor, or a friend 
>declaration, or rewriting the container serialisation functions for each  T.

I'm sorry I don't see a difference.  Your function:

> template<class Archive ar, class T>
> T *load_construct(Archive & ar,  void * pt,  unsigned int file_version)
> {
>     T *t = new( pt ) T();
>     try {
>         ar >> *t;
>    } catch (...) {
>         t->T::~T();
>         throw;
>     }
>     return t;
>}

has the same limitations as the current system.

a) if the default constructor is private - a friend declaration will be necessary
- otherwise not.
b) if there is no default constructor - this function will have to be overridden
for each T without a default constructor

But - . In the current system - collection loading will have to be overridden 
for each T as well.

So, at long last,  I believe I see the motivation of factoring out "load-construct" so that
for classes without a default constructor we don't have to override in two places. 
I will consider this some more. 

Robert Ramey