[Boost-users] [Serialization]Why does serialization make use of two step initialization?

From: tankbattle (tankbattle_at_[hidden])
Date: 2006-10-10 08:27:54

I'm using boost::serialization now and, indeed, it is very powerful, especially 
in type identification and object tracking, which make me very convenient. 
However, I think the lack of construction-time deserialization a pitfall. 
Usually the semantic of constructor is that either the constructed object is 
valid or an exception is thrown. However, boost::serialization require 
programmers provide a default constructor to construct an empty object and a 
load method (or serialize) to really initialize the object. Such a mechanism 
cannot prevent from invoking load method other than one time. What’s more, the 
default constructor usually lacks information to completely initialize the 
object, sometimes, it is even impossible to initialize. For instance,
class B
{
public:
        void operator() (){…}
}
class A
{
private:
        B* pB;
        boost::thread m_theThread;//make use of pB->operator() as the entry 
point
};
In the code above, pB in A cannot be correctly initialized in default 
constructor, but m_theThread MUST be initialized there. What entry point should 
we provide to m_theThread?
I think serialization mechanism (especially deserialization part) should be 
provided for constructors. A tricky problem is how can constructor-time 
deserialization be coherent with that in “load” method and however can we 
eliminate duplicate code is another issue.