Yea I had thought about this but haven't tried it yet. I am working on this tonight. I have another question that could help me. Is their a documentation available on exactly what is serialized in the archive, the class format and related stuff seem to be serialized as a list of numbers (at least in text archive it appears so, forgive me if I am wrong). What is serialized exactly for each class (beside what the user specifies of course!)?
<br><br>If found that on a forum but I am not sure how relevant it is (from basic_archive.cpp) :<br><br>//////////////////////////////////////////////////////////////////////
<br>
//
<br>
// class_information is stored as
<br>
//
<br>
// class_id* // -1 for a null pointer
<br>
// if a new class id
<br>
// [
<br>
// exported key - class name*
<br>
// tracking level - always/never
<br>
// file version
<br>
// ]
<br>
//
<br>
// if tracking
<br>
// [
<br>
// object_id
<br>
// ]
<br>
//
<br>
// [ // if a new object id
<br>
// data...
<br>
// ]
<br>
//
<br>
// * required only for pointers - optional for objects
<br><br>Thank you!<br><br><div><span class="gmail_quote">On 10/19/07, <b class="gmail_sendername">Robert Ramey</b> <<a href="mailto:ramey@rrsd.com">ramey@rrsd.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff">
<div><font face="Arial" size="2">I've never thought about this, but my first attempt
would be something like the following:</font></div>
<div><font face="Arial" size="2"></font> </div>
<div><font face="Arial" size="2">template<class Archive></font></div>
<div><font face="Arial" size="2">void load(Archiv &ar , C &c, const unsigned
int version){</font></div>
<div><font face="Arial" size="2"> if(version <
4>)</font></div>
<div><font face="Arial" size="2">
ar >> boost::serialization::base_object<A>(c);</font></div>
<div><font face="Arial" size="2"> else</font></div>
<div><font face="Arial" size="2">
ar >> boost::serialization::base_object<B>(c);</font></div>
<div><font face="Arial" size="2">}</font></div>
<blockquote style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px; padding-left: 5px; margin-left: 5px; margin-right: 0px;">
<div>"Fred Lupien" <<a href="mailto:fred.lupien@gmail.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">fred.lupien@gmail.com</a>> wrote in
message <a href="news:32e6d6bf0710190708x45191057ld2a23a92399f59e4@mail.gmail.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">news:32e6d6bf0710190708x45191057ld2a23a92399f59e4@mail.gmail.com
</a>...</div><span class="q">
<div>Hello,<br><br> we are currently
implementing serialization versioning using boost and I am curious to know if
their is a way to support a changing class hierarchy. Let's say C derives from
A for a while and then a change requires C to derive from B instead, which
derives from A. Is it possible to support such a change provided we know what
default values are needed for the new class? I tried and even if don't
serialize anything in class C I get stream errors because I believe boost
saves some base info for each class. When it tries to reload those value from
a old stream, obviously it desynchronizes it because the values are not in the
stream. So is their a way around this? <br><br>Also is it possible to support
the removal of a class. If, for exemple C derives from B which in turn derives
from A and suddenly B is removed. Is their a way to deal with this without
invalidating all previously saved data? </div>
<div> </div></span>
<div><font face="Arial" size="2">*** I doubt it. If you want to load old
archives, you have know how much to "skip" over. The only thing that
MIGHT be possible</font></div>
<div><font face="Arial" size="2">is something like:</font></div><font face="Arial" size="2"></font></blockquote>
<blockquote style="border-left: 2px solid rgb(0, 0, 0); padding-right: 0px; padding-left: 5px; margin-left: 5px; margin-right: 0px;">
<div>
<div><font face="Arial" size="2">template<class Archive></font></div>
<div><font face="Arial" size="2">void load(Archiv &ar , C &c, const
unsigned int version){</font></div>
<div><font face="Arial" size="2"> if(version <
4>){</font></div>
<div><font face="Arial" size="2"> class a;
//no longer used</font></div>
<div><font face="Arial" size="2"> ar >>
a;</font></div>
<div><font face="Arial" size="2"> // throw
away old data on leaving scope</font></div>
<div><font face="Arial" size="2"> }</font></div>
<div><font face="Arial" size="2"> else</font></div>
<div><font face="Arial" size="2">
ar >> boost::serialization::base_object<B>(c);</font></div><span class="q">
<div><font face="Arial" size="2">}</font></div><br><br>Thank you for your help!<br clear="all"><br>-- <br>Fr�d�rick Martel-Lupien<br>�tudiant en G�nie
Informatique<br>Universit� de Sherbrooke<br><a href="mailto:fred.lupien@gmail.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">fred.lupien@gmail.com</a> </span></div>
<p>
</p><hr>
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fred.lupien@gmail.com</a>