C++ iterate through a template Map - c++

Question

When I have a template class which contains template map and a const_iterator declared as in the following code by typedef, how can I iterate through the elements of the map outside the class, f.e in main to print them on the output?
template<class K, class V>
class template_map{
private:
typedef typename std::map<K,V> TMap;
TMap my_map;
public:
typedef typename TMap::const_iterator const_iterator;
...
};
int main()
{
template_Map<int,double> Map1 //suppose that contains elements
?
}
Update: Can the typedef iterator be used outside the class? If yes in what way?

Answer 1

You need to define member functions on your template that would return iterators:
template<class K, class V>
class template_map{
private:
typedef typename std::map<K,V> TMap;
TMap my_map;
public:
typedef typename TMap::const_iterator const_iterator;
const_iterator begin() const { return my_map.begin(); }
const_iterator end() const { return my_map.end(); }
};
Then:
int main()
{
template_map<int, int> m;
// Populate map...
// Then iterate...
for (auto i = m.begin(); i != m.end(); i++)
{
}
}
However, I am unsure what your adding to std::map here, why not just use it as is?

Answer 2

Add begin() and end() members to template_Map (both const and non-const variants).
const_iterator begin() const {
return my_map.begin();
}
const_iterator end() const {
return my_map.end();
}
iterator begin() {
return my_map.begin();
}
iterator end() {
return my_map.end();
}
I added non-const versions just for interface completeness, it may not be required in your case.
Than in main:
typedef template_Map<x, y> template_MapXY;
template_MapXY Map1;
...
for ( template_MapXY::const_iterator it( Map1.begin() ), end( Map1.end() ); it != end; ++ it ) {
...
}

Answer 3

I don't understand why you want to wrap a map class with another one. Why don't you std::map itself?
Iteration over a std::map is usually done like this:
for(std::map<mykey, myvalue>::iterator it = mymap.begin(); it != mymap.end(); ++it)
{
somevar = it->first; // <<--- points to your key
someothervar = it->second; // points to your value
}