C ++ - 从抽象基指针调用派生的函数 [英] C++ - calling derived function from abstract base pointer
问题描述
我一直在试图创建一个基于继承的TCP服务器模型，并取得了不同的成功。这些服务器由单独管理，它的任务是关闭这些服务器和其他简单的维护功能：
class TCPServer {
public：
TCPServer（）;
〜TCPServer（）;
void Bind（TCPDaemon * daemon）{
if（！daemon-> IsRunning（））{
throw TCPBindException（Daemon is inactive）;
}
//如果不使用端口，则将此守护程序绑定到
if（this-> servers.count（daemon-> port（））= = 0）{
this-> servers [daemon-> port（）] = daemon;
...
} else {
throw TCPBindException（Port is taken）;
}
}
void Shutdown（）{
MASON :: UINT16 i;
for（i = 0; i servers.size（）; i ++）{
this-> Shutdown（（* this-> servers.begin（））。 ;
}
}
无关闭（unsigned short port）{
if（this-> servers.count（port））{
if（this-> servers [port] - > IsRunning（））{
this-> servers [port] - > Stop
}
delete this-> servers [port];
this-> servers.erase（port）;
}
}
private：
std :: map< unsigned short，TCPDaemon *>服务器;
};
TCPDaemon类的Stop（）函数是一个纯虚函数。我的问题是，当Shutdown（）函数被调用时，它试图调用这个纯虚拟而不是派生类的版本。如何强制它做正确的事？
提前感谢
不包括之前的TCPDaemon代码，它来自一个TCPSocket类（我已经检查是100％工作，是相当不言自明的）。这是：
类TCPDaemon：public TCPSocket {
public：
TCPDaemon（unsigned short port） {
this-> _enabled = false;
this-> _host.ipaddr（INADDR_ANY）;
this-> _host.port（port）;
this-> paused = false;
struct sockaddr_in opts = this-> _host.Compile（）;
#ifdef PLATFORM_WINDOWS
WSADATA wsaData;
if（WSAStartup（0x0202，& wsaData））{
throw TCPDaemonException（无法启动WSA）;
}
#endif
this-> raw_socket = socket（AF_INET，SOCK_STREAM，0）;
if（this-> raw_socket< = 0）{
throw TCPDaemonException（无法创建套接字）;
}
if（int status = bind（this-> raw_socket，（sockaddr *）& opts，sizeof（sockaddr）））{
printf（error [ ％i] \r\\\
，status）;
throw TCPDaemonException（无法绑定到端口）;
}
if（listen（this-> raw_socket，5））{
throw TCPDaemonException（Failed to listen on port）;
}
this-> _enabled = true;
}
virtual〜TCPDaemon（）{
this-> Shutdown（）;
}
virtual void Start（）= 0;
virtual void Run（TCPSocket *）= 0;
virtual void Stop（）= 0;
unsigned short port（）{
return this-> host（）。port（）;
}
bool IsRunning（）{
return this-> _enabled;
}
TCPSocket * Accept（）{
SOCKET客户端;
struct sockaddr client_addr;
int len = sizeof（client_addr）;
client = accept（this-> raw_socket，& client_addr，& len）;
return new TCPSocket（client，& client_addr）;
}
void Shutdown（）{
}
private：
bool _enabled;
bool paused;
};
这里是一个示例派生服务器及其创建方法：
class EchoServer：public TCPDaemon {
public：
EchoServer（MASON :: UINT16 port）：TCPDaemon（port）{
}
〜EchoServer（）{}
virtual void Start（）{
}
virtual void Run TCPSocket * client）{
printf（RUN\r\\\
）;
Accessor< TCPSocket> acc_client = client;
acc_client-> Write（Accessor< Blob>（new Blob（std :: string（hello！）））））;
acc_client-> Disconnect（）;
}
virtual void Stop（）{
}
};
myTCPServer-> Bind（new EchoServer（8008））;
[edit + 1]我想问题归结为这是）：
我有一个基类的std :: map，TCPDaemon，它有一个纯虚拟/抽象函数Stop（）。看起来当我通过地图中的一个条目调用Stop（）时，它试图调用TCPDaemon :: Stop（），而不是覆盖函数EchoServer :: Stop（）。这是问题吗？
我不确定这是否是您遇到的问题，在下面的函数中肯定有一个问题。
void Shutdown（）{
MASON :: UINT16 i;
for（i = 0; i servers.size（）; i ++）{
this-> Shutdown（（* this-> servers.begin（））。 ;
}
}
在每个循环迭代器之后， i 会增加一个，而 size 会减少，所以你只需要ShutDown一半的服务器。
您可以执行以下任一操作：
code> void Shutdown（）{
MASON :: UINT16 i;
std :: size_t nrServers = this-> servers.size（）;
for（i = 0; i
}
}
或者，我更喜欢，因为它更好地显示代码的意图：
void Shutdown（）{
while（！this-> servers.empty ）{
this-> Shutdown（（* this-> servers.begin（））。
}
}
I have been trying to create a TCP Server model based on inheritance, with varying success. These servers are managed by a singleton whose task it is to shut these servers down and other simple maintenance functions:
class TCPServer {
public:
TCPServer();
~TCPServer();
void Bind(TCPDaemon *daemon) {
if(!daemon->IsRunning()) {
throw TCPBindException("Daemon is inactive");
}
// if the port is not taken, bind this daemon to it
if(this->servers.count(daemon->port())==0) {
this->servers[daemon->port()]=daemon;
...
} else {
throw TCPBindException("Port is taken");
}
}
void Shutdown() {
MASON::UINT16 i;
for(i=0;i<this->servers.size();i++) {
this->Shutdown((*this->servers.begin()).first);
}
}
void Shutdown(unsigned short port) {
if(this->servers.count(port)) {
if(this->servers[port]->IsRunning()) {
this->servers[port]->Stop();
}
delete this->servers[port];
this->servers.erase(port);
}
}
private:
std::map<unsigned short, TCPDaemon*> servers;
};
The TCPDaemon class's Stop() function is a pure virtual. My problem is that when the Shutdown() function is called, it is attempting to call this pure virtual instead of the derived class' version. How can I force it to do the right thing?
Thanks in advance
[edit] sorry I did not include the TCPDaemon code before, it derives from a TCPSocket class (which I have checked to be 100% working and is fairly self-explanatory). Here it is:
class TCPDaemon: public TCPSocket {
public:
TCPDaemon(unsigned short port) {
this->_enabled=false;
this->_host.ipaddr(INADDR_ANY);
this->_host.port(port);
this->paused=false;
struct sockaddr_in opts=this->_host.Compile();
#ifdef PLATFORM_WINDOWS
WSADATA wsaData;
if(WSAStartup(0x0202, &wsaData)) {
throw TCPDaemonException("Failed to start WSA");
}
#endif
this->raw_socket=socket(AF_INET, SOCK_STREAM, 0);
if(this->raw_socket<=0) {
throw TCPDaemonException("Failed to create socket");
}
if(int status=bind(this->raw_socket, (sockaddr*)&opts, sizeof(sockaddr))) {
printf("error [%i]\r\n", status);
throw TCPDaemonException("Failed to bind to port");
}
if(listen(this->raw_socket, 5)) {
throw TCPDaemonException("Failed to listen on port");
}
this->_enabled=true;
}
virtual ~TCPDaemon() {
this->Shutdown();
}
virtual void Start()=0;
virtual void Run(TCPSocket*)=0;
virtual void Stop()=0;
unsigned short port() {
return this->host().port();
}
bool IsRunning() {
return this->_enabled;
}
TCPSocket *Accept() {
SOCKET client;
struct sockaddr client_addr;
int len=sizeof(client_addr);
client=accept(this->raw_socket, &client_addr, &len);
return new TCPSocket(client, &client_addr);
}
void Shutdown() {
}
private:
bool _enabled;
bool paused;
};
and here is a sample derived server and its method of creation:
class EchoServer: public TCPDaemon {
public:
EchoServer(MASON::UINT16 port): TCPDaemon(port) {
}
~EchoServer() {}
virtual void Start() {
}
virtual void Run(TCPSocket *client) {
printf("RUN\r\n");
Accessor<TCPSocket> acc_client=client;
acc_client->Write(Accessor<Blob> (new Blob(std::string("hello!"))));
acc_client->Disconnect();
}
virtual void Stop() {
}
};
myTCPServer->Bind(new EchoServer(8008));
[edit+1] I think what the problem boils down to is this (i could easily be wrong): I have a std::map of the base class, TCPDaemon, which has a pure virtual/abstract function Stop(). It appears that when I call Stop() through one of the entries in the map, it is attempting to call TCPDaemon::Stop(), as opposed to the overriding function EchoServer::Stop(). Could this be the issue? If so, how do I resolve it?
I'm not sure if this is the problem you're seeing, but there's certainly a problem in the following function.
void Shutdown() {
MASON::UINT16 i;
for(i=0;i<this->servers.size();i++) {
this->Shutdown((*this->servers.begin()).first);
}
}
After each loop iterator, i will increase by one AND size will decrease, so you'll only ShutDown half your servers. Maybe keeping some open is the cause of further errors.
You could do either:
void Shutdown() {
MASON::UINT16 i;
std::size_t nrServers = this->servers.size();
for(i=0;i<nrServers;i++) {
this->Shutdown((*this->servers.begin()).first);
}
}
or, which I would prefer as it better shows the intention of the code:
void Shutdown() {
while (!this->servers.empty()) {
this->Shutdown((*this->servers.begin()).first);
}
}
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