Re: [Boost-users] Serialization and reading from a const object

From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2006-05-25 06:33:36

Robert Ramey wrote:
> Thorsten Ottosen wrote:

>>I understand the need for ensuring
>>
>>1. no invalid archives are created.
>>2. no data is lost.
>>3. no runtime errors occur.
> 
> 
>>but there has to be a better way, even if it means
>>3 becomes a runtime exception.
> 
> 
> Hmmm - to ensure 2) that would have to occur
> on archive save - I'm not even sure that's possible.
> Even so it lot harder to track down than the current setup.

These three bullets are taken from your documentation of what teh 
benefits of your current setup is. I just don't get why serializing a
non-const object can lead to them.

>>Somehow the information of a class and how it is serialized must be
>>localized ***in one place only*** so one programmer can't ruin the
>>archieve of another programmer without his knowlegde.
> 
> 
> In my view all that should be in the header module which declares the
> class.  This is always possible and that's what I always do. It's
> always grouped together in one place in one module.  
> Personally
> I don't understand why everyone doesn't do it that way.  Maybe
> we need a macro which specifes all the serialization traits for a type
> like BOOST_CLASS_TRAITS(tracking, abstract, etc...) rather
> than just letting people sprinkle them will-nilly all over their code.

Write a section in your tutorial called "Serialization best practices".
If all that is needed is to always put serialization "derectives"
together with the class declaration, that's a pretty cheap fix.

>>BTW: I'm ok with
>>
>>T * t;
>>ar >> t;
>>
>>failing (just make it part of the toturial). That's completely
> 
> 
>>different from reading from an object.
> 
> 
> Hmm - I'm doubtful that would be a popular idea.

Your docs state that this will fail when tracking has been set to something!

> But, you want to establish a different default policy for your own company, 

no, I don't want to do that. I want people to use your library and not 
turn it down because they can't get hello world to work.

> The argument that people don't/won't read the documentation doesn't evoke
> much sympathy from me.

Well, people read documentation, but there is a limit to how much
new stuff a programmers brain can taker per day. Not many read it all
and remember it all.

>  On one hand we want to permit someone to make
> an egregious error so that he won't have to read the manual to understand
> the nature of his error. I don't buy it.  In the code where the static 
> assertion
> occurs there is a pointer to the explanation in the manual. 

I certainly couldn't find that. Otherwise I wouldn't have asked you 
personally.

> I want everyone to be successful using the library - even if they complain
> that it requires them to write good code.

If good code means "put serialization meta information with the class 
declaration", I agree. If you mean

a << add_const( obj );

I don't agree.

-Thorsten