c++ - mistake in vector showing -

this question has answer here:

• what object slicing? 15 answers

i have 2 simple classes. want vector show result, number not showed. on other hand, when try result without vector, result show. can me? thank you.

#include <iostream> #include <string> #include <vector> #include <iterator>  using namespace std;   template<typename t> class 1 { protected:     t word;     t word2;  public:     one() {word = "0"; word2 = "0";}     one(t w, t w2) {word = w; word2 = w2;}     virtual const void show() {cout << word << endl; cout << word2 << endl;} };  template<typename t> class 2 : public one<t> { private:     int number; public:     two() {number = 0;}     two(t w, t w2, int n) : one(w,w2) {number = n;}     virtual const void show () {cout << word << endl; cout << word2 << endl; cout << number << endl; } };   int main () {     one<string> *idk;     two<string> *something = new two<string>("asd","aa",1);     idk = something;      idk->show(); // ok - asd, aa, 1      vector<one<string>> arr;     arr.push_back(*idk);      arr.at(0).show(); // wrong - asd,aa     return 0; } 

you storing one<string> instances instead pointers them one<string>*.

since object stored totally in vector cell, there no polymorphism object suffers slicing: additional feature inherits one in instance placing inside vector discarded.

try vector<one<string>*> pointer stored , problem doesn't occur. mind that, manage memory, using smart pointer when working stl collections wise choice.