C ++：在迭代器向量中使用erase

Question

I'm experiencing a problem using the erase function in C++.

I have the following structure:

typedef std::map<std::string,TreeElement> ObjMap;
class TreeElement {
    public:
        ObjMap::const_iterator parent;
        std::vector<ObjMap::const_iterator > children;
}

Now I'm trying to remove a TreeElement from the list of children of its parent using the erase function.

//Remove from parent
SegmentMap::const_iterator parent = segment->second.parent;
std::vector<SegmentMap::const_iterator >::const_iterator it = parent->second.children.begin();
for(;((*it)->first != segment->first) && (it != parent->second.children.end()); it++);
parent->second.children.erase(it); //Compilation fails

This gives an error during compilation indicating it can't convert

__gnu_cxx::__normal_iterator<const std::_Rb_tree_const_iterator<std::pair<const std::basic_string<char>, TreeElement> >*, std::vector<std::_Rb_tree_const_iterator<std::pair<const std::basic_string<char>, TreeElement> > > >

to

__gnu_cxx::__normal_iterator<std::_Rb_tree_const_iterator<std::pair<const std::basic_string<char>, TreeElement> >*, std::vector<std::_Rb_tree_const_iterator<std::pair<const std::basic_string<char>, TreeElement> > > >

Is there any way to fix this? I tried using an iterator instead of a const_iterator but this just moved the compilation error to

std::vector<SegmentMap::const_iterator >::iterator it = parent->second.children.begin();

Clarification: I know the erase function expects a non-const iterator. I'm looking for a way to create this non-const iterator without changing the declaration of parent and children in the TreeElement class.

Answer 1

Parent is const iterator, therefore parent->second is const, therefore parent->second.children is const, therefore parent->second.children.begin() returns const iterator.

erase expects a non-const iterator.

Answer 2

You cannot do erase() when using const_iterator . The purpose of const_iterator is to prohibit modification of the vector in any way, including erasing elements through it. You should use simply iterator and then fix that compilation error.

Then that compilation error is because you are trying to assign a const_iterator to a non-const iterator . If you modify and make parent a non-const iterator , the error should go away.