C++11 shared_ptr智能指针

#include<iostream>
using namespace std;
#include<memory>
class test {
public:
  test(int no) {
    this->no = no;
    cout << "调用构造函数: " << no << endl;
  }
  ~test() {
    cout << "调用析构函数: " << no << endl;
  }
private:
  int no;
};

shared_ptr<test>sp;
  shared_ptr<test>sp2(new test(1));
  //use_count :当前管控同一个对象的智能指针对象
  cout<<"sp.use_count:" << sp.use_count() << endl;//0
  cout<<"sp2.use_count:" << sp2.use_count() << endl;//1
  sp = sp2;
  cout << "----sp = sp2----" << endl;
  cout << "sp.use_count:" << sp.use_count() << endl;//2
  cout << "sp2.use_count:" << sp2.use_count() << endl;//2
  shared_ptr<test>sp3(sp);
  cout << "---shared_ptr<test>sp3(sp)---" << endl;
  cout << "sp.use_count:" << sp.use_count() << endl;//3
  cout << "sp2.use_count:" << sp2.use_count() << endl;//3
  cout << "sp3.use_count:" << sp3.use_count() << endl;//3
  //sp.use_count() == sp2.use_count() == sp3.use_count()
  system("pause");

//数组对象管理
  shared_ptr<test[]>arr(new test[5]{ 11, 22, 33, 44, 55 });

//仿函数
class DestructTest {
public:
  void operator()(test* t) {
    cout << "调用DestructTest... " << endl;
    delete t;
  }
};

shared_ptr<test>sp(new test(666), DestructTest());

//使用make_shared初始化对象,分配内存效率更高
  // make_shared<类型>(参数)
  shared_ptr<string>s = make_shared<string>("ABC");
  shared_ptr<string>s2;
  s2 = make_shared<string>("abc");

//主动释放对象
  shared_ptr<string>s = make_shared<string>("ABC");
  s = NULL;
  //或
  // s = nullptr;