断开Qt5中的lambda函数 [英] Disconnecting lambda functions in Qt5

问题描述

是否可以断开lambda函数？如果是，如何？

Is it possible to disconnect a lambda function? And if "yes", how?

根据 https：// qt -project.org/wiki/New_Signal_Slot_Syntax 我需要使用从QObject :: connect方法返回的 QMetaObject :: Connection ，但是如何将该对象传递给lambda函数？

According to https://qt-project.org/wiki/New_Signal_Slot_Syntax I need to use a QMetaObject::Connection which is returned from the QObject::connect method, but then how can I pass that object to the lambda function?

伪代码示例：

QMetaObject::Connection conn = QObject::connect(m_sock, &QLocalSocket::readyRead, [this](){
    QObject::disconnect(conn); //<---- Won't work because conn isn't captured

    //do some stuff with sock, like sock->readAll();
}

推荐答案

如果直接捕获 conn 你需要捕获一个智能指针：

If you capture conn directly, you're capturing an uninitialised object by copy, which results in undefined behaviour. You need to capture a smart pointer:

std::unique_ptr<QMetaObject::Connection> pconn{new QMetaObject::Connection};
QMetaObject::Connection &conn = *pconn;
conn = QObject::connect(m_sock, &QLocalSocket::readyRead, [this, pconn, &conn](){
    QObject::disconnect(conn);
    // ...
}

或使用共享指针， p>

Or using a shared pointer, with slightly greater overhead:

auto conn = std::make_shared<QMetaObject::Connection>();
*conn = QObject::connect(m_sock, &QLocalSocket::readyRead, [this, conn](){
    QObject::disconnect(*conn);
    // ...
}

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