Need help with map (c++, STL)
- by Mike Dooley
Hi folks!
Actually I'm new to C++. I tried something out (actually the map container) but it doesn't work the way I assumed it will... Before posting my code, I will explain it shortly.
I created 3 classes:
ClassA
ClassDerivedA
ClassAnotherDerivedA
The two last ones are derived from "ClassA".
Further I created a map:
map<string,ClassA> test_map;
I put some objects (from Type ClassDerivedA and ClassAnotherDerivedA) into the map. Keep in mind: the mapped value is from type "ClassA". This will only work because of Polymorphism. Finally I created an iterator which runs over my map and compares the user input with my keys in the map. If they match, it will call a specific method called "printOutput".
And there is the Problem:
Although i declared "printOutput" as "virtual" the only method called is the one from my base class, but why?
and here is the code:
#include <iostream>
#include <map>
using namespace std;
class ClassA
{
public:
virtual void printOutput() { cout << "ClassA" << endl; }
};
class ClassDerivedA : public ClassA
{
public:
void printOutput() { cout << "ClassDerivedA" << endl; }
};
class ClassAnotherDerivedA: public ClassA
{
public:
void printOutput() { cout << "ClassAnotherDerivedA" << endl; }
};
int main()
{
ClassDerivedA class_derived_a;
ClassAnotherDerivedA class_another_a;
map<string,ClassA> test_map;
test_map.insert(pair<string,ClassA>("deriveda", class_derived_a));
test_map.insert(pair<string,ClassA>("anothera", class_another_a));
string s;
while( cin >> s )
{
if( s != "quit" )
{
map<string,ClassA>::iterator it = test_map.find(s);
if(it != test_map.end())
it->second.printOutput();
}
else
break;
}
}
Blockquote
