编译器编译一个\'io_service_\'变量，显示为：不能出现在常量表达式中
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我创建了一个ServerService命名空间，用于包含类名称server_datetime。 Server_datetime类作为Boost示例的教程，但是我通过使用模板参数将io_service（boost :: asio :: io_service）和端点（tcp :: endpoint（tcp :: v4（），SIZE_DATA））对象插入模板来改进了server_datetime类。我遵循以下示例：
using boost::asio::ip::tcp;
namespace ServerService{
template<typename Service, typename Endpoint>
class server_datetime {
public:
server_datetime(){
acceptor_(service_, endpoint_);
for(;;)
{
tcp::socket socket(Service);
acceptor_.accept(socket);
std::string message = make_daytime_string;
boost::system::error_code ignored_error;
boost::asio::write(socket, boost::asio::buffer(message),boost::asio::transfer_all(), ignored_error);
}
}
std::string make_daytime_string(){
std::time_t now = std::time(0);
return std::ctime(&now);
}
virtual ~server_datetime();
private:
tcp::acceptor acceptor_;
Service service_;
Endpoint endpoint_;
};
}
#include \"server_datetime.hpp\"
using namespace std;
using boost::asio::ip::tcp;
int main() {
const boost::asio::io_service io_service_;
const int SIZE_DATA = 13;
ServerService::server_datetime<io_service_, tcp::endpoint(tcp::v4(),SIZE_DATA) > server;
cout << \"\" << endl; // prints
return 0;
}
..\\src\\connectk.cpp: In function \'int main()\':
..\\src\\connectk.cpp:10: error: \'io_service_\' cannot appear in a constant-expression
..\\src\\connectk.cpp:10: error: \'boost::asio::ip::tcp::v4()\' cannot appear in a constant-expression
..\\src\\connectk.cpp:10: error: a function call cannot appear in a constant-expression
..\\src\\connectk.cpp:10: error: template argument 1 is invalid
..\\src\\connectk.cpp:10: error: template argument 2 is invalid
..\\src\\connectk.cpp:10: error: invalid type in declaration before \';\' token
没有找到相关结果
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3 个回复
辽躺
您忘记了（），应为：迪擅哨乘傅
琶竞捆栓
namespace ServerService{ // Put \'using\' declarations inside the namespace, // to avoid polluting the global namespace using boost::asio::ip::tcp; using boost::asio::io_service; // Not a template - pass runtime objects as constructor arguments class server_datetime { public: server_datetime(io_service & service, tcp::endpoint const & endpoint) : // Initialise members in an initialiser list acceptor_(service, endpoint), service_(service) {} // Put the main loop in a separate function; it\'s rather odd // to have a constructor that doesn\'t return. void run(){ for(;;) { // Argument must be the object service_, not the type Service tcp::socket socket(service_); acceptor_.accept(socket); std::string message = make_daytime_string(); // missing parentheses boost::system::error_code ignored_error; boost::asio::write(socket, boost::asio::buffer(message),boost::asio::transfer_all(), ignored_error); } } std::string make_daytime_string(){ std::time_t now = std::time(0); return std::ctime(&now); } // No need for a virtual destructor - this class is not polymorphic private: boost::asio::io_service & service_; // must be a reference - io_service is not copyable tcp::acceptor acceptor_; // No need to store the endpoint - it\'s only used to initialise acceptor_. }; } int main() { using boost::asio::ip::tcp; // can\'t be const if you want to use it boost::asio::io_service io_service_; // renamed SIZE_DATA and given it the same type as the constructor argument const unsigned short port = 13; ServerService::server_datetime server(io_service_, tcp::endpoint(tcp::v4(),port)); server.run(); // no need to explicitly return zero, unless you want to. }