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  1. #include <string>
  2. #include <list>
  3. #include <iostream>
  4. #include <stdexcept>
  5.  
  6. #include <memory>
  7.  
  8. using namespace std;
  9.  
  10. class Connection {
  11.     std::string name;
  12. public:
  13.     const std::string& getName() const { return name; }
  14.  
  15.     explicit Connection(const std::string& n):name(n) {
  16.         std::cout << "Connection " << name << std::endl;
  17.     }
  18.  
  19.     ~Connection() {
  20.         name = '~' + name;
  21.         std::cout << "~Connection " << name << std::endl;
  22.     }
  23. };
  24.  
  25. typedef shared_ptr<Connection> ptr_t;
  26.  
  27. class ConnectionPool {
  28.     std::list<ptr_t> connections;
  29.  
  30.     // Этот класс предназначен для демонстрации первого варианта создания deleter (get1)
  31.     class ConnectionReleaser {
  32.         std::list<ptr_t>& whereToReturn;
  33.         ptr_t connectionToRelease;
  34.     public:
  35.         ConnectionReleaser(std::list<ptr_t>& lst, const ptr_t& x):whereToReturn(lst), connectionToRelease(x) {}
  36.         ~ConnectionReleaser()
  37.         {
  38.         	cout << "~ConnectionReleaser()" << endl;
  39.         	cout << connectionToRelease.get() << endl;
  40.         	if (0 == connectionToRelease.get())
  41.         	{
  42.         		cout << "NULL" << endl;
  43.         	}
  44.         	else
  45.         	{
  46.         		cout << connectionToRelease->getName() << endl;
  47.         	}
  48.         }
  49.  
  50.         void operator()(Connection*) {
  51.             whereToReturn.push_back( connectionToRelease );
  52.             std::cout << "get1: Returned connection " << connectionToRelease->getName() << " to the list" << std::endl;
  53.  
  54.             // Закомментируйте след. строку и обратите внимание на разницу в выходной печати
  55.             //connectionToRelease.reset();
  56.         }
  57.     };
  58.  
  59.     // Эта функция предназначена для демонстрации второго варианта создания deleter (get2)
  60.     static void releaseConnection(std::list<ptr_t>& whereToReturn, ptr_t& connectionToRelease) {
  61.         whereToReturn.push_back( connectionToRelease );
  62.         std::cout << "get2: Returned connection " << connectionToRelease->getName() << " to the list" << std::endl;
  63.  
  64.         // Закомментируйте следующую строку и обратите внимание на разницу в выходной печати
  65.         connectionToRelease.reset();
  66.     }
  67.  
  68.     ptr_t popConnection() {
  69.         if( connections.empty() ) throw std::runtime_error("No connections left");
  70.         ptr_t w( connections.back() );
  71.         connections.pop_back();
  72.         return w;
  73.     }
  74. public:
  75.     ptr_t get1() {
  76.         ptr_t w = popConnection();
  77.         std::cout << "get1: Taken connection " << w->getName() << " from list" << std::endl;
  78.         ptr_t r( w.get(), ConnectionReleaser( connections, w ) );
  79.         return r;
  80.     }
  81.  
  82.     ptr_t get2() {
  83.         ptr_t w = popConnection();
  84.         std::cout << "get2: Taken connection " << w->getName() << " from list" << std::endl;
  85.         ptr_t r( w.get(), bind(&releaseConnection, ref(connections), w ));
  86.         return r;
  87.     }
  88.  
  89.     void add(const std::string& name) {
  90.         connections.push_back( ptr_t(new Connection(name)) );
  91.     }
  92.  
  93.     ConnectionPool() {
  94.         std::cout << "ConnectionPool" << std::endl;
  95.     }
  96.  
  97.     ~ConnectionPool() {
  98.         std::cout << "~ConnectionPool" << std::endl;
  99.     }
  100. };
  101.  
  102. int main() {
  103.     weak_ptr<Connection> weak1;
  104.     weak_ptr<Connection> weak2;
  105.     {
  106.         ConnectionPool cp;
  107.         cp.add("One");
  108.         cp.add("Two");
  109.  
  110.         ptr_t p1 = cp.get1();
  111.         weak1 = p1;
  112.         //ptr_t p2 = cp.get2();
  113.         //weak2 = p2;
  114.     }
  115.     std::cout << "weak1.expired()" << weak1.expired() << endl;
  116.     std::cout << "Here the ConnectionPool is out of scope, but weak_ptrs are not" << std::endl;
  117.     return 0;
  118. }
Success #stdin #stdout 0s 3444KB
comments (?)
stdin
copy 
Standard input is empty
stdout
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ConnectionPool
Connection One
Connection Two
get1: Taken connection Two from list
~ConnectionReleaser()
0x8fcd078
Two
~ConnectionReleaser()
0x8fcd078
Two
~ConnectionReleaser()
0x8fcd078
Two
~ConnectionReleaser()
0x8fcd078
Two
~ConnectionReleaser()
0x8fcd078
Two
get1: Returned connection Two to the list
~ConnectionPool
~Connection ~One
weak1.expired()1
Here the ConnectionPool is out of scope, but weak_ptrs are not
~ConnectionReleaser()
0x8fcd078
Two
~Connection ~Two
https://ideone.com/yRpnJJ
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
secret

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