对象回收实验

对象被释放时，成员变量（不是new出来的）会被自动释放

#include <iostream>
#include <memory>
using namespace std;
class Cat {

public:
  int age;
  ~Cat() { cout << "~Cat" << endl; }
};
class Person {

public:
  int age;

  Cat cat;
  ~Person() { cout << "~person" << endl; }
};
void test1(Cat &cat) {}
int main() {
  // { shared_ptr<Person> ptr = make_shared<Person>(); }
  Person *p = new Person();

  delete p;
}

打印：

~person
~Cat

vector push_back会发生拷贝构造

#include <iostream>
#include <memory>
#include <vector>
using namespace std;
class Cat {

public:
  int age;
  ~Cat() { cout << "~Cat" << endl; }
  Cat() { cout << "Cat" << endl; }
  Cat(const Cat &cat) { cout << "Cat copy" << endl; }
};
class Person {

public:
  int age;

  Cat cat;
  ~Person() { cout << "~person" << endl; }
};
int main() {
  // { shared_ptr<Person> ptr = make_shared<Person>(); }
  Person p;
  {
    vector<Person> v;
    v.push_back(p);
  }
  cout << "vector over !" << endl;
}

打印

Cat
Cat copy
~person
~Cat
vector over !
~person
~Cat