c++ - 当两个类相互引用时编译C++

我试图围绕连接指针编写一个简单的包装器，该包装器在销毁包装器时将其返回到池中，但是它不会编译，因为ConnectionPool和AutoConn需要彼此声明。

我试图使用正向减速，但是没有用。我该如何解决？ (使用g++)

class Connection {};

class ConnectionPool
{
    Connection *m_c;
public:
    AutoConn getConn()
    {
        return AutoConn(this, m_c); // by value
    }

    void releaseConnection(Connection *c)
    {
    }
};

class AutoConn
{
    ConnectionPool* m_pool;
    Connection *m_connection;
public:
    AutoConn(ConnectionPool* pool, Connection *c) : m_pool(pool), m_connection(c) {}
    ~AutoConn()
    {
        m_pool->releaseConnection(m_connection);
    }
};

最佳答案

前向声明和声明与循环依赖成员的定义分离的组合是可行的。例如:

class Connection {};
class ConnectionPool ;

class AutoConn
{

    ConnectionPool* m_pool;
    Connection *m_connection;
public:
    AutoConn(ConnectionPool* pool, Connection *c) : m_pool(pool), m_connection(c) {}
    ~AutoConn() ;  // Not defined here because it accesses unknown members of class Connection
} ;

class ConnectionPool
{
    Connection *m_c;
public:
    AutoConn getConn()
    {
        return AutoConn(this, m_c); // by value
    }

    void releaseConnection(Connection *c)
    {
    }
};

// Definition of destructor with class Connection member dependencies.
AutoConn::~AutoConn()
{
    m_pool->releaseConnection(m_connection);
}

关于c++ - 当两个类相互引用时编译C++，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/2447310/