#include <iostream>

class A { // Contained class.
public:
    A(int i) : a_number_(i) {}
    void print() const { std::cout << a_number_ << "n"; }
private:
    int a_number_;
};

class A_Container { // Container class.
public:
    ~A_Container() { delete a_; }
    A_Container(const A& a) : a_(new A(a)) { std::cout << "I was called!n"; }
    const A& getA() const { return *a_; }
private:
    A* a_;
};

void foo(const A_Container& container) { // This func takes a container...
    container.getA().print();
}

int main() {
    A a(147);
    foo(a); // ...but I'm passing it the contained class.
    return 0;
}

I was called!
147