Non-const lvalue reference to type '_wrap_iter<pointer>' cannot bind to a value of unrelated type

Question

I was wondering whether someone could help me fix this error. I've looked it over and can't see what possible is going wrong. The compiler is point to the line

    while (_hasNextAttribute(it1, it2, thisAttribute))

of the following code

bool HtmlProcessor::_processTag(std::string::const_iterator it1, const std::string::const_iterator it2, node & nd)
{
    /*
       [it1, it2): iterators for the range of the string
               nd: node in which classes and ids of the tage are stored

        Returns true or false depending on whether a problem was encountered during the processing.
    */


    std::string elementType("");
    while (_elementTypeChars.find(*it1) != std::string::npos && it1 != it2) elementType.push_back(*it1++);
    if (elementType.empty()) return false;
    nd.element_type = elementType;


    std::vector<std::pair<std::string, std::string>> attributes;
    const std::pair<std::string, std::string> thisAttribute;
    while (_hasNextAttribute(it1, it2, thisAttribute))
        attributes.push_back(thisAttribute);



    return true;
}

bool HtmlProcessor::_hasNextAttribute(std::string::iterator & it1, const std::string::iterator & it2, const std::pair<std::string, std::string> attrHolder)
{

....

and is saying

Non-const lvalue reference to type '_wrap_iter' cannot bind to a value of unrelated type '_wrap_iter'

Answer 1

When I try to compile your code, the compiler (VS 2013) complains const iterator it1 cannot be converted to std::string::iterator & . The exact error message:

1>Cpp-Test.cpp(36): error C2664: 'bool _hasNextAttribute(std::_String_iterator>> &,const std::_String_iterator>> &,const std::pair)' : cannot convert argument 1 from 'std::_String_const_iterator>>' to 'std::_String_iterator>> &'

Basically you have two options:

• Option 1: it1 and it2 are non-const

   bool _processTag(std::string::iterator it1, const std::string::iterator it2, node & nd) 

• Option 2: _hasNextAttribute() takes const iterators

   bool _hasNextAttribute(std::string::const_iterator & it1, const std::string::const_iterator & it2, const std::pair<std::string, std::string> attrHolder) 

Everything compiles fine for me when I apply one of these options (not both of course).

The choice is whether you want const iterators here. _hasNextAttribute() looks like an info method to me, ie providing info, not changing anything. So I guess const iterator should be OK.