[英]Boost asio deadline timer completing immediately (C++)
下面的代码会立即打印“已连接”到控制台,而不是 10 秒后。 为什么是这样? 这与我传递print
回调的方式有关吗?
void print(const boost::system::error_code& e) {
std::cout << "connected!" << std::endl;
}
class WebSocketSession {
public:
WebSocketSession(asio::io_context &io_context) : io_context_(io_context) {}
void connect() {
boost::asio::deadline_timer
timer(io_context_, boost::posix_time::seconds(10));
timer.async_wait(&print);
}
private:
asio::io_context &io_context_;
};
class WebSocketClient {
public:
WebSocketClient(asio::io_context &io_context) : io_context_(io_context) {}
std::unique_ptr<WebSocketSession> exec() {
auto session = std::make_unique<WebSocketSession>(io_context_);
session->connect();
return session;
}
private:
asio::io_context &io_context_;
};
int main() {
asio::io_context io_context;
WebSocketClient client{io_context};
std::unique_ptr<WebSocketSession> session = client.exec();
io_context.run();
return 0;
}
正如评论中提到的, deadline_timer
被过早销毁,因为它是一个局部变量,从而取消了 I/O 操作。
如果我们添加一些错误处理,我们将看到报告的实际错误:
void print(const boost::system::error_code& e) {
if (e.failed())
std::cout << "error: " << e.message() << std::endl;
else
std::cout << "connected!" << std::endl;
}
印刷:
error: The I/O operation has been aborted because of either a thread exit or an application request
一个可能的解决方法是将deadline_timer
移动为WebSocketSession
的成员:
class WebSocketSession {
public:
WebSocketSession(boost::asio::io_context& io_context) : io_context_(io_context),
timer_(io_context, boost::posix_time::seconds(10)) {}
void connect() {
timer_.async_wait(&print);
}
private:
boost::asio::io_context& io_context_;
boost::asio::deadline_timer timer_;
};
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