Find Key in XML with Boost - c++

Question

I am using boost for the first time within an old code base that we have
iptree children = pt.get_child(fieldName);
for (const auto& kv : children) {
boost::property_tree::iptree subtree = (boost::property_tree::iptree) kv.second ;
//Recursive call
}
My problem is sometimes the fieldName doesn`t exist in the XML file and I have an exception
I tried :
boost::property_tree::iptree::assoc_iterator it = pt.find(fieldName);
but I dont know how to use the it I can`t use: if (it != null)
Any help please will be appreciated
I am using VS 2012
If it`s very complicated is there any other way to read a XML with nested nodes? I am working on that since 3 days
This is an Example of the XML
<?xml version="1.0" encoding="utf-8"?>
<nodeA xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<nodeA.1>This is the Adresse</nodeA.1>
<nodeA.2>
<node1>
<node1.1>
<node1.1.1>Female</node1.1.1>
<node1.1.2>23</node1.1.2>
<node1.1.3>Engineer</node1.1.3>
</node1.1>
<node1.2>
<node1.2.1>Female</node1.2.1>
<node1.2.2>35</node1.2.2>
<node1.2.3>Doctors</node1.2.3>
</node1.2>
</node1>
</nodeA.2>
<nodeA.3>Car 1</nodeA.3>
</nodeA>

Answer 1

Use pt.get_child_optional(...) to prevent an exception. pt.find(...) returns an iterator which compares true to pt.not_found() on failure.
EDIT: How to use boost::optional<--->
boost::optional< iptree & > chl = pt.get_child_optional(fieldname);
if(chl) {
for( auto a : *chl )
std::cerr << ":" << a.first << ":" << std::endl;
}