CODEWITHSUNDEEP
c++qt
Nowax
Nowax

Reputation: 347

How can I emit signal form another class?

How can i emit signal from another class? In my implementation shown below I've got "unresolved external symbol error" when I try to emit signal in SerialPort::open method. Code, head file of main window:

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    std::shared_ptr<SerialPort> serialPort;

private slots:
    void labelchange();
private:    
    Ui::MainWindow *ui;

};

and the cpp file:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow),
    serialPort(std::shared_ptr<SerialPort>(new SerialPort))
{
    ui->setupUi(this);
    connect(serialPort.get(), SIGNAL(opened()),this,SLOT(labelchange()));
}
void MainWindow::labelchange()
{
    ui->testinLabel->setText("signal connected to slot");
}

and the other class method when i try emit signal: head file:

class SerialPort : public QObject
{
public:
    SerialPort();
    void open()

signals:
    void serial_opened();
}

and cpp file:

void SerialPort::open()
{
    emit serial_opened();
}

Upvotes: 0

Views: 905

Answers (2)

Maxim Makhun
Maxim Makhun

Reputation: 2231

SerialPort shall contain Q_OBJECT marco like this:

class SerialPort : public QObject
{
    Q_OBJECT
public:
    SerialPort();
    void open()

signals:
    void serial_opened();
}

Also please check your .pro file and check whether you added your SerialPort.h under HEADERS section.

Upvotes: 1

BeniBela
BeniBela

Reputation: 16907

This is just normal signal emitting from a class. Not "from another" class.

You are missing the Q_OBJECT macro, QObject do not really work with out it:

class SerialPort : public QObject
{
  Q_OBJECT
public:
    SerialPort();
    void open()

signals:
    void serial_opened();
}

And you need to have the file processed by moc. (happens automatically, if the files are listed in the .pro file)

Upvotes: 1

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