CODEWITHSUNDEEP
c++qt
Hi-Angel
Hi-Angel

Reputation: 5659

Qt: "No such signal" error

I have a simple code; here I've two buttons, I press the first one and it shows a MsgBox. Then I press the "Okay", and it should call a connected action written in a second button, but it doesn't. Instead I get an error:

Object::connect: No such signal QMessageBox::buttonClicked(QMessageBox::Ok)
Object::connect:  (receiver name: 'OpenFile_Bttn')

The code:

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_OpenFile_Bttn_clicked(){
    QFileDialog::getOpenFileName(this,tr("Open file"), "", tr(""));//Open a dialog "OpenFile"
}

void MainWindow::on_pushButton_clicked(){
    QMessageBox msgBox;
    msgBox.setText("Push button to choose a file");
    //Connect clicking button in MsgBox to an action in OpenFile_Bttn button
    QWidget::connect(&msgBox,SIGNAL(buttonClicked(QMessageBox::Ok)),
            ui->OpenFile_Bttn, SLOT(on_OpenFile_Bttn_clicked()));
    msgBox.exec();//Show MsgBox
}

Also I found an interesting thing, that the error message appears when a MsgBox popup, but not when I click the button "Ok" inside the MsgBox.

Upvotes: 2

Views: 1488

Answers (2)

AngryDuck
AngryDuck

Reputation: 4607

If you do this instead you get a compiler error, that way you can see something is wrong at compile instead of runtime error

QObject::connect(msgBox, &QMessageBox::buttonClicked, ui->OpenFile_Bttn, &QPushButton::clicked);

out of interest the above code is untested and probably wont compile but basicallt just do sender, signal, reciever, slot but use their class object to select signal and slots like shown above and then you will get an easier to spot compile error that tells you what could be wrong

Upvotes: 2

Sebastian Lange
Sebastian Lange

Reputation: 4029

No need for signals here, exec returns the button clicked.

void MainWindow::on_OpenFile_Bttn_clicked(){
    QFileDialog::getOpenFileName(this,tr("Open file"), "", tr(""));//Open a dialog "OpenFile"
}

void MainWindow::on_pushButton_clicked(){
    QMessageBox msgBox;
    msgBox.setText("Push button to choose a file");
    //Connect clicking button in MsgBox to an action in OpenFile_Bttn button
    if(msgBox.exec() == QMessageBox::Ok)
    {
      on_OpenFile_Bttn_clicked();
    }
}

If you want to use custom buttons you can still call msgBox.buttonClicked() after exec to find out which button was clicked.

Upvotes: 5

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