如何在Qt信号和插槽使用枚举 [英] How to use enums in Qt signals and slots

问题描述

我在使用 enum 类型的信号时遇到了一些麻烦。基本上我有两个类，状态机和线程处理状态机。当状态改变时，我想发送一个带有新状态的信号。我还想使用枚举表示状态。在我完整的代码中，状态机在一个单独的共享库中实现，但下面的代码给出了完全相同的错误。

I have some trouble with using enum types in signals. Basicly I have two classes, a state machine and a thread handling the state machine. When the state is changed I want to send a signal with the new state. I also want to represent the state using an enum. In my full blown code the state machine is implemented in a separate shared library, but the code below gives the exact same error.

当我运行代码，我得到以下行为：

When I run the code I get the following behaviour:

kotte@EMO-Ubuntu:sigenum $ ./sigenum 
Object::connect: No such slot MyThread::onNewState(state)
Test signal 
Test signal 
...

$ b b

我的示例代码中有四个文件： statemachine.h ， statemachine.cpp ， main.h 和 main.cpp 。主函数只是启动线程，线程然后创建 StateMachine 的一个实例，并处理来自 StateMachine 的信号。我对Qt很新，所以我有点困惑，当我意识到你必须用 Q_ENUMS 包含枚举并注册类型系统。所以这是完全可能的，我犯了一些菜鸟的错误

I have four files in my sample code: statemachine.h, statemachine.cpp, main.h and main.cpp. The main function simply starts the thread, the thread then creates an instance of the StateMachine and processes signals from the StateMachine. I am pretty new to Qt, so I was a bit puzzled when I realised that you have to enclose the enum with Q_ENUMS and register it with the type system. So It's fully possible that I've made some rookie mistake

下面的代码有点长，但我想它是类似于我的真正的代码尽可能。

The code below is a bit long, but I wanted it to be as similar to my real code as possible.

statemachine.h 如下所示：

// statemachine.h
#ifndef _STATEMACHINE_H
#define _STATEMACHINE_H

#include <QtCore>

class StateMachine : public QObject
{
    Q_OBJECT
    Q_ENUMS(state)

public:
    enum state {S0, S1, S2};

    void setState(state newState);

signals:
    void stateChanged(state newState);
    void testSignal(void);
};

Q_DECLARE_METATYPE(StateMachine::state);

#endif

其实现方式如下：

// statemachine.cpp
#include <QtCore>

#include "statemachine.h"

void StateMachine::setState(state newState)
{
    emit stateChanged(newState);
    emit testSignal();
}

线程定义为

// main.h
#ifndef _MAIN_H
#define _MAIN_H

#include <QtCore>

#include "statemachine.h"

class MyThread : public QThread
{
    Q_OBJECT

private:
    void run(void);

private slots:
    void onNewState(StateMachine::state);
    void onTestSignal(void);

private:
    StateMachine *myStateMachine;
};

#endif

其实现如下：

// main.cpp
#include <QtCore>
#include <QApplication>

#include "statemachine.h"
#include "main.h"

void MyThread::run()
{
    myStateMachine = new StateMachine();

    qRegisterMetaType<StateMachine::state>("state");

    // This does not work
    connect(myStateMachine, SIGNAL(stateChanged(state)),
            this, SLOT(onNewState(state)));

    // But this does...
    connect(myStateMachine, SIGNAL(testSignal()),
            this, SLOT(onTestSignal()));

    forever {
        // ...
        myStateMachine->setState(StateMachine::S0);
    }
}

void MyThread::onTestSignal()
{
    qDebug() << "Test signal";
}

void MyThread::onNewState(StateMachine::state newState)
{
    qDebug() << "New state is:" << newState;
}

推荐答案

如果我将 stateChanged（）的声明更改为

signals:
    void stateChanged(StateMachine::state newState);

并注册

qRegisterMetaType<StateMachine::state>("StateMachine::state");

，并在 connect 语句

connect(myStateMachine, SIGNAL(stateChanged(StateMachine::state)),
        this, SLOT(onNewState(StateMachine::state)));

如果没有drescherjm的输入就不能解决这个问题，谢谢： - ）

Wouldn't have solved this without the input from drescherjm, thanks :-)

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