提升property_tree用于存储指针

Question

Is it possible to store pointers to objects in boost property trees, and then use an iterator to retrieve the data? I'm trying to do something like:

property_tree::ptree pt;
pt.put<CGUICrateElement*>("1.2.3.4", new MyObject() );
//... more tree construction here...

and then recursively itererate through all the tree nodes with something like:

property_tree::ptree::iterator iter = treeNode.begin();
property_tree::ptree::iterator iter_end = treeNode.end();

for ( ; iter != iter_end; ++iter )
{
MyObject *obj = lexical_cast<MyObject*>(iter->second.data());
    //... etc 

The problem is I get the error lexical_cast.hpp:1112: error: no match for 'operator>>' in 'stream >> output' on the lexical cast line.

and adding the following to MyObject doesn't help

friend std::istream& operator>>(std::istream& in, MyObject& obj){ return in; }

I've also tried c casts and dynamic casts to no avail.

Is using pointers even possible inside a ptree? I'm about to just create my own tree structure as a workaround by I figured I'd ask here first.

Cheers.

Answer 1

Adding an operator>> for a reference to MyObject won't help when you're actually trying to lexical_cast to a pointer to MyObject. You could conceivably create an operator>>(std::istream&, MyObject*&) . However, remember that property_tree is designed for reading configuration from text files, so you'll have the joy of converting your object to and from text.

Don't use property_tree as a generic data structure. Internally it will be expecting to deal with text.

Answer 2

It is looking a lot like you wanted a serialization solution. I covered some ground (including storing through pointers) in this post:

copying and repopulating a struct instance with pointers

This example also shows serialization to XML, collections containing (potentially) duplicated pointers. On deserialization, the pointers will be reconstructed faithfully (including the duplication).