C++连接未被触发

Question

我正试着玩C++中的基本信号/插槽。

下面是我的Network-Manager，，它将触发事件：

class NetworkManager : public QObject {
Q_OBJECT
public:
    explicit NetworkManager(QApplication* application);
    void OnFinished(QNetworkReply *reply);
    ...
signals:
    void OnReceived();
};

在Display-Manager，中，该类将接收以下事件：

class DisplayManager : public QObject{
Q_OBJECT
public:
    explicit DisplayManager(QApplication *app);
    void ChangeWallPaper();
public slots:
    void ReceiveData();
};

我正试着从另一个班联系起来：

Manager::Manager(QApplication *application, NetworkManager networkManager, DisplayManager displayManager)
: networkManager(application),displayManager(application) {
    ...
    connect(&networkManager, &NetworkManager::OnReceived, &displayManager, &DisplayManager::ReceiveData);
}

在这些类的实现中：

void DisplayManager::ReceiveData() {
    std::cout << "being called" << std::endl;// to check if this is being called
}

void NetworkManager::OnFinished(QNetworkReply *reply) {
    OnReceived(); // to trigger
}
// OnReceived() not implemented as it just a signal

我在这里遗漏了什么，为什么ReceiveData没有被调用？

Answer 1

以下是解决方案：

Manager::Manager(QApplication *application,
                 NetworkManager _networkManager,
                 DisplayManager _displayManager)
        : networkManager(application)
        , displayManager(application)
{
    ...
    connect(&networkManager, &NetworkManager::OnReceived,
            &displayManager, &DisplayManager::ReceiveData);
}

Answer 2

考虑一下您的Manager构造函数..。

Manager::Manager(QApplication *application,
                 NetworkManager networkManager,
                 DisplayManager displayManager)
    : networkManager(application)
    , displayManager(application)
{
    ...
    connect(&networkManager, &NetworkManager::OnReceived,
            &displayManager, &DisplayManager::ReceiveData);
}

将本地作用域变量networkManager和displayManager的地址传递给connect。当这些临时变量在构造函数完成时超出作用域时，连接就会被销毁。

尝试通过引用或指针传递networkManager和displayManager。