How can one determine whether an XMLDocument object is newly created and has never loaded any data?

[Mr-zhangyh]

When I try to use doc.empty() to determine whether the document is empty, the returned value is always 0. After doc loads an XML document, the return value remains 0 regardless of whether I call doc.reset().
My expectation is as follows:
When doc is created and no XML document has been loaded, or after doc calls the reset() function, the return value of doc.empty() should be 1;
When an XML document is loaded, doc.empty() should return 0.
Thus, I checked the implementation of the doc.empty() function, which is: return !_root;.
Since you have encapsulated the doc object, the empty() function should be used to judge whether the doc document has loaded data, rather than judging whether the doc object has been constructed by its constructor.
I wonder if this is a bug. Could you please help clarify this, expert? Thank you!

    cout << "test xml_document:\t\n";
    pugi::xml_document doc;
    
    cout << "doc is empty : " << doc.empty() << endl;
    doc.load_file("E:/BCProject/VS2022Projects/OpenWord/OpenWord/empty/[Content_Types].xml");
    cout << doc.first_child().name() << endl;
    cout<<"doc is empty : "<< doc.empty()<<endl;
    doc.reset();
    
    cout << doc.first_child().name() << endl;

    cout << "doc is empty : " << doc.empty() << endl;

[zeux]

xml_document::empty is misleading, it's just xml_node::empty that is inherited. It means "is this node a null node" (see https://pugixml.org/docs/manual.html#dom.cpp); a document is never a null node.

What you want is "does the document have no nodes?", which can be checked via doc.first_child().empty().

[Mr-zhangyh]

Haha! I just came up with the idea of modifying the source code to make the xml_document class override the empty() member function of xml_node. This way, the functions will have consistent functionality: the empty() function of the xml_document class is used to determine whether the doc document is an empty document, while the empty() function of xml_node is used to check if an xml_node is an empty object.
Alternatively, we can directly useif (doc.first_child()) {}to determine whether the doc is empty.
Thanks !!!

[Mr-zhangyh]

On second thought, to play it safe, I’ll use your recommended method for judgment rather than adding a new overloaded function – modifying the source code would create potential pitfalls down the line.