QT Future Watcher With mail Client - c++

Question

Hi I am using the code from here https://github.com/xcoder123/SimpleSmtp_SSL_QT5/tree/master/smtp_attachements to send mail from my qt application and it's work fine, but when I use future wacht to run the mail sender in another thread it does'nt work
QFuture<void> f4 = QtConcurrent::run(this,&MainWindow::sendMail); // this doesnot work
//sendMail(); //this work
Here is the mainWindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "QSettings"
#include "QFuture"
#include "QtConcurrent/QtConcurrent"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->sendBtn, SIGNAL(clicked()),this, SLOT(test()));
connect(ui->exitBtn, SIGNAL(clicked()),this, SLOT(close()));
connect(ui->browseBtn, SIGNAL(clicked()), this, SLOT(browse()));
}
void MainWindow::browse()
{
files.clear();
QFileDialog dialog(this);
dialog.setDirectory(QDir::homePath());
dialog.setFileMode(QFileDialog::ExistingFiles);
if (dialog.exec())
files = dialog.selectedFiles();
QString fileListString;
foreach(QString file, files)
fileListString.append( "\"" + QFileInfo(file).fileName() + "\" " );
ui->file->setText( fileListString );
}
void MainWindow::test(){
QFuture<void> f4 = QtConcurrent::run(this,&MainWindow::sendMail);
//sendMail();
}
void MainWindow::sendMail()
{
Smtp* smtp = new Smtp(ui->uname->text(), ui->paswd->text(), ui->server->text(), ui->port->text().toInt());
connect(smtp, SIGNAL(status(QString)), this, SLOT(mailSent(QString)));
if( !files.isEmpty() )
smtp->sendMail(ui->uname->text(), ui->rcpt->text() , ui->subject->text(),ui->msg->toPlainText(), files );
else
smtp->sendMail(ui->uname->text(), ui->rcpt->text() , ui->subject->text(),ui->msg->toPlainText());
}
void MainWindow::mailSent(QString status)
{
if(status == "Message sent")
QMessageBox::warning( 0, tr( "Qt Simple SMTP client" ), tr( "Message sent!\n\n" ) );
}
MainWindow::~MainWindow()
{
delete ui;
}
and mainWindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "smtp.h"
#include <QtWidgets/QMessageBox>
#include <QFileDialog>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void sendMail();
void mailSent(QString);
void browse();
void test();
private:
Ui::MainWindow *ui;
QStringList files;
};
#endif // MAINWINDOW_H
The smtp class is as shown here, I haven't touch anything
https://github.com/xcoder123/SimpleSmtp_SSL_QT5/blob/master/smtp_attachements/smtp.h
https://github.com/xcoder123/SimpleSmtp_SSL_QT5/blob/master/smtp_attachements/smtp.cpp
Any one know why it's not working when running in a thread using future watcher.
Thanks
Haris

Answer 1

The problem is that QtConcurrent::run just runs a single function, in your case sendMail, in a separate thread. As soon as this function returns, the thread is not active anymore and the slots in Smtp will not be called.
Either change your function sendMail to not return until the mail is sent or use a QThread and move Smtp* stmp to it using QObject::moveToThread.