How to iterate a C++ map of maps - c++

Question

I have a map of map
std::map< int, std::map<string, double> > myMap;
std::map< int, std::map<string, double> >::iterator itr;
Iterating it with:
itr = myMap.find(nodeI);
if (itr == myMap.end())
{
exit(1) ;
}
results in the error:
error: no match for âoperator=â in
âitr = ((const PushList*)this)->PushList::myMap.std::map&lt:_Key, _Tp, _Compare, _Alloc>::find
[with _Key = int, _Tp = std::map&lt:std::basic_string&lt:char, std::char_traits&lt:char>,
std::allocator&lt:char> >, double, std::less&lt:std::basic_string&lt:char,
std::char_traits&lt:char>,
std::allocator&lt:char> > >, std::allocator&lt:std::pair&lt:const std::basic_string&lt:char,
std::char_traits&lt:char>, std::allocator&lt:char> >, double> > >, _Compare =
std::less&lt:int>, _Alloc =
std::allocator&lt:std::pair&lt:const int, std::map&lt:std::basic_string&lt:char,
std::char_traits&lt:char>,
std::allocator&lt:char> >, double, std::less&lt:std::basic_string&lt:char,
std::char_traits&lt:char>,
std::allocator&lt:char> > >, std::allocator&lt:std::pair&lt:const std::basic_string&lt:char,
std::char_traits&lt:char>, std::allocator&lt:char> >, double> > > > >](((const
int&)((const int*)((int*)nodeI))))â
How can I iterate the map of map?

Answer 1

From the error you posted it can be seen that you are doing this from within a class member const function. Is there any chance that myMap happens to be a member of that class? If so, what you want is to use const_iterator instead. You should do it anyways, since you are not expecting to modify the contents of the iterated elements.