Example of using shared_ptr with inheritance

shared_ptr_inheritance_example.cpp

#include<iostream>
#include<memory>
#include<vector>

using namespace std;

class A {
  private:
    int val;
  public:
    A(int _v) : val(_v) {}
    int getValue() const { return val; }
    virtual void print() = 0;
};

class B : public A {
  public:
    B(int a) : A(a) {}
    virtual void print() override {
      cout << "This is inherited class B" << endl;
    }
};

class C : public A {
  public:
    C(int a) : A(a) {}
    virtual void print() override {
      cout << "This is inherited class C" << endl;
    }
};

class D : public A {
  public:
    D(int a) : A(a) {}
    virtual void print() override {
      cout << "This is inherited class D" << endl;
    }
};


static void printAll(vector<A*> vecA) {
  for(auto& I : vecA)
    I->print();
}

static void printAll(vector<shared_ptr<A>> vecA) {
  for(auto& I : vecA)
    I->print();
}

int main () {
  B* b0 = new B(10);

  cout << "The value is: " << b0->getValue() << endl;
  b0->print();

  cout << "=====================================" << endl;

  B* b1 = new B(100);
  C* c1 = new C(101);
  D* d1 = new D(102);
  
  vector<A*> a {b1,c1,d1};
  printAll(a);

  cout << "=====================================" << endl;

  auto b3 = make_shared<B>(200);
  auto c3 = make_shared<C>(200);
  auto d3 = make_shared<D>(200);
  vector<shared_ptr<A>> b {c3,b3,d3};
  printAll(b);
  return 0;
}