CODEWITHSUNDEEP
c++qtqprocess
Dmon
Dmon

Reputation: 218

QProcess saving to QTextEdit

What I'm trying to do is launch a program within another program using QProcess and then save the output from the launched program into a QTextEdit of the launcher program. Every time I launch this program I want it to add more text to the QTextEdit. Now I get the program to launch but then after the text is supposed to be written it crashes. Here is the code:

#include <QWidget>
#include <QPushButton>
#include <QTextEdit>
#include <QProcess>
#include <QVBoxLayout>
#include <QApplication>

class Widget : public QWidget
{
    Q_OBJECT
    QTextEdit* text;
public:
    Widget() : text(new QTextEdit) {
        QPushButton* addBtn = new QPushButton("Add Module");
        text->setReadOnly(true);
        QVBoxLayout* layout = new QVBoxLayout(this);
        layout->addWidget(addBtn,0);
        layout->addWidget(text);
        connect(addBtn,SIGNAL(clicked()),SLOT(launchModule()));
    }
    Q_SLOT void launchModule() {
        QString program = "C:/A2Q2-build-desktop/debug/A2Q1.exe";
        QProcess *myProcess = new QProcess(this);
        connect(myProcess, SIGNAL(finished(int)), SLOT(finished()));
        connect(myProcess, SIGNAL(error(QProcess::ProcessError)), SLOT(finished()));
        myProcess->start(program);
    }
    Q_SLOT void finished() {
        QProcess *process = qobject_cast<QProcess*>(sender());
        QString out = process->readAllStandardOutput(); // will be empty if the process failed to start
        text->append(out);
        delete process;
    }
};

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    Widget w;
    w.show();
    app.exec();
}

#include "main.moc"

Upvotes: 0

Views: 777

Answers (2)

Kuba hasn&#39;t forgotten Monica
Kuba hasn&#39;t forgotten Monica

Reputation: 98425

It's crashing because you're deleting the sender object while inside a slot. Instead of delete process, you should

process->deleteLater();

For logging purposes you should be using QPlainTextEdit instead of a QTextEdit. The former is faster. You're prematurely pessimizing by using the latter. Alas, even QPlainTextEdit becomes abysmally slow if you're sending about 100 lines/s (at least on Qt 4.8). If you want a really fast log view, you'll need to use QListWidget, with a caveat, or roll your own.

I have a complete example of how to send to and receive from a process in another answer.

Upvotes: 3

Tyler Jandreau
Tyler Jandreau

Reputation: 4335

The process is crashing because you're deleting the parent from within the finished slot.

Also, it's probably easier to do something like this:

QObject::connect(process, SIGNAL(readyReadStandardOutput()), this, SLOT(getOutput()));

instead of using the finished() slot. But that's more personal preference than anything.

Upvotes: 1

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