c++ - 信号未在此范围内声明/未定义对 class::method 的引用

Question

我一直在尝试在 Qt 应用程序中整理自定义信号，但似乎无法编译它。本质上，我有一个窗口，其中有一个槽来处理按钮按下(slotCalibrate())，另一个槽用于接收消息并通过 QTextEdit 将它们输出到屏幕(slotMessage())。这两个函数单独工作时效果很好。

这里是Window.cpp，slotCalibrate()当前正在将预制数据发送到Output类。在最终的设计中，slotCalibrate()将在某些硬件上激活校准过程，其结果将是发送到Output.cpp的数据

#include "window.h"
#include "output.h"
#include <QPushButton>
#include <QTextEdit>
#include <QApplication>
#include <string>

using namespace std;

Window::Window(QWidget *parent) :
    QWidget(parent)
{
    setFixedSize(640, 480);

    calButton = new QPushButton("Calibrate", this);
    calButton->setGeometry(280, 20, 80, 30);
    calButton->setToolTip("Press to zero connected transducers.");

    connect(calButton, SIGNAL(clicked()), this, SLOT(slotCalibrate()));

    quitButton = new QPushButton("Quit", this);
    quitButton->setGeometry(550, 440, 80, 30);

    connect(quitButton, SIGNAL(clicked()), QApplication::instance(), SLOT(quit()));

    readout = new QTextEdit(this);
    readout->setReadOnly(1);
    readout->setPlainText("Testing, testing, 1, 2, 3.\n");
    readout->setGeometry(10, 70, 620, 360);
}

void Window::slotCalibrate()
{
    string sn[5] = {"1234", "2463", "7821", "5027", "5981"};
    Output *op = new Output();
    op->writeMessage(1, 5, sn);
    //I also tried the following with exactly the same result
    //Output op;
    //op.writeMessage(1, 5, sn);
}

void Window::slotMessage(string message)
{
    QString qstr = QString::fromStdString(message); //Convert from string to QString
    readout->append(qstr);                          //Print message to screen
}

我试图按下按钮来调用output.cpp的构造函数，然后调用函数writeMessage来构造消息并将其发送到window.cpp中的slotMessage

#include "output.h"
#include <string>
#include <sstream>

using namespace std;

Output::Output(QWidget *parent) :
    QWidget(parent)
{
    connect (this, SIGNAL(sendMessage(string)), parentWidget(), SLOT(slotMessage(string)));
}

//void sendMessage(string)
//{

//}

void writeMessage(int cat, int count, string sn[])
{
    int i;
    stringstream ss;
    switch (cat)
    {
        case 1 : //Case where calibration of one or more nodes was successful
            ss << count << " transducers were successfully calibrated.\n Their serial numbers are:";
            for (i=0; i<cat; i++)
            {
                ss << "\n" << sn[i];
            }
            break;
        case 2:  //Case where calibration of one or more nodes failed
            ss << "One or more transducers failed to calibrate.";
            break;
        case 3:  //Case where no config file is found
            ss << "WARNING! Could not find 'params.config'. The default values will be used for calibration.";
                  break;
    }
    emit sendMessage(ss.str());
}

不幸的是，对于这样的代码，编译器对我大喊大叫。它说: “sendMessage”未在此范围内声明

我已在头文件中将 sendMessage 声明为信号，并且我认为信号不需要在代码中实现。

尽管如此，我还是决定尝试实现一个名为 sendMessage 的空函数。这消除了编译器错误，但引入了另一个错误。在 window.cpp 中调用 op.writeMessage() 时，出现错误: “对‘Output::writeMessage(int, int, std::string*)’的 undefined reference ”

我还尝试在输出构造函数内调用writeMessage，但出现了相同的错误。

我完全迷失了，并且已经在这个问题上工作了几天，所以任何帮助将不胜感激。

为了完整起见，这里分别是头文件 window.h 和 output.h:

窗口.h

#ifndef WINDOW_H
#define WINDOW_H

#include <QWidget>
#include <string>

class QPushButton;
class QTextEdit;
class Window : public QWidget
{
    Q_OBJECT
public:
    explicit Window(QWidget *parent = 0);
    QTextEdit *readout;
private:
    QPushButton *calButton;
    QPushButton *quitButton;

signals:

public slots:
    void slotCalibrate();

private slots:
    void slotMessage(std::string);
};

#endif // WINDOW_H

输出.h

#ifndef OUTPUT_H
#define OUTPUT_H

#include <QWidget>
#include <QObject>
#include <string>

class Output : public QWidget
{
    Q_OBJECT
public:
    explicit Output(QWidget *parent = 0);
    void writeMessage(int, int, std::string[]);
signals:
    void sendMessage(std::string);
public slots:

};

#endif // OUTPUT_H

Answer 1

当然这是行不通的。您定义了 writeMessage() 函数，但将其定义为全局函数。您必须在定义前添加“Output::”。