App crashes when closed

Padawan

Can someone explain to me why this app runs fine but crashes when i close it, is it because i ran it on a WIN 7 PC?

#include "widget.h"
#include "ui_widget.h"
#include <QJsonDocument>
#include <QJsonArray>
#include <QJsonObject>
#include <QJsonValue>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
    ,netManager(new QNetworkAccessManager(this))
    ,netReply(nullptr)
    ,dataBuffer(new QByteArray)
{
    ui->setupUi(this);
    pres = new QString("Here's a List of our enemies and their co-ordinates Mr.President!!");
    timer = new QTimer(this);
    timer->setInterval(20);
    connect(timer,SIGNAL(timeout()),this,SLOT(updateText()));
}

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


void Widget::on_fetchButton_clicked()
{
    QNetworkRequest netReq{QUrl("https://jsonplaceholder.typicode.com/users")};
    netReply = netManager->get(netReq);
    timer->start();
    connect(netReply,&QNetworkReply::readyRead,this,&Widget::readData);
    connect(netReply,&QNetworkReply::finished,this,&Widget::finishRead);
}

void Widget::readData()
{
    dataBuffer->append(netReply->readAll());
}

void Widget::finishRead()
{
    if(netReply->error())
        qDebug() << "Error - " << netReply->errorString();
    else{
        //CONVERT THE RECEIVED DATA FROM A QBYTEARRAY TO A JSON DOC
        auto doc = QJsonDocument::fromJson(*dataBuffer);
        //BREAK DOWN THE DOCUMENT INTO JSON-ARRAYS AND OBJECTS FOR DATA RETRIEVAL
        auto jsonArray = doc.array();
        for(int i{0}; i < jsonArray.size(); ++i){
            auto jObj = jsonArray.at(i).toObject();
            auto name = jObj.value("name").toString();
            QJsonObject address = jObj.value("address").toObject().value("geo").toObject();
            auto lat = address.value("lat").toString();
            auto lng = address.value("lng").toString();
            qDebug() << name << " " << lat << " " << lng;
            ui->listWidget->addItem(QString(name + " (%1,%2)").arg(lat,lng));
        }
    }
}

void Widget::updateText()
{
    if(ui->lineEdit->text().length() == pres->length()){
        qDebug() << "Stopped!";
        timer->stop();
        return;
    }
    if(ui->lineEdit->text().isEmpty()){
        ui->lineEdit->setText("H");
        return;
    }
    auto txt = ui->lineEdit->text();
    txt.append(pres->at(i));
    ui->lineEdit->setText(txt);
    ++i;
}

Padawan

Header

#pragma once

#include <QWidget>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QByteArray>
#include <QDebug>
#include <QTimer>
QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

private slots:
    void on_fetchButton_clicked();
    void readData();
    void finishRead();
    void updateText();

private:
    Ui::Widget *ui;
    QNetworkAccessManager *netManager;
    QNetworkReply *netReply;
    QByteArray * dataBuffer;
    QTimer *timer;
    QString *pres;
    int i{1};
};

JonB

Run it in a debugger and see if you get a stack trace when it crashes?
Reduce your code to something minimal, e.g. is all of that JSON code of the slightest relevance, do you need line edits (or indeed any UI)?

Padawan

@JonB it was there before the lineEdit, and the JSON code is the main thing, i'm just learning how to parse a JSON file and get data from it...i will do the stack trace stuff

Christian Ehrlicher

Use a debugger, see where it crashes and fix it.

Padawan

@Christian-Ehrlicher

Padawan

doesnt look like it crashes in the code itself, and i dont even understand what that stuff is

SGaist

Hi,

@Padawan said in App crashes when closed:

QByteArray * dataBuffer;
QString *pres;

Neither of these needs to be stored on the heap.

@Padawan said in App crashes when closed:

int i{1};

You might want to reserve that for the for loops. It's a bit too generic and your use of it in the code is not really clear.

JonB

@Padawan
The pane you are interested in is not the big one but the one in the bottom-left corner. That shows the stack trace, where the code was executing at the moment of the crash. Although memory mess-ups like this could emanate from elsewhere and be spurious, it looks like the issue lies in SSL. Somehow related to your get request to https. That's where I would look, nothing to do with the JSON or UI. Is your version of OpenSSL for Qt good?