Slots in the second window?

RootLearner

In my main window, I have

    QString movie = ui->movie_name->text();
    connect(this, SIGNAL(send(QString)), List, SLOT(get_movie(QString)));
    emit send(movie);

And in the List window, I need to have that slot. My lists.h is:

    QString getMovieName(QString movie)
    {
        return movie;
    }

And in my lists.cpp, I have:

    QString a;
    a = getMovieName(m);
    ui->label->setText(a);
}

But, the 'm' variable cannot be used in it as it is not declared. How do I assign the movie name to the variable 'a' in lists.cpp?

jsulm

@RootLearner Please read https://doc.qt.io/qt-5/signalsandslots.html
I don't understand what you are doing? Where is your slot get_movie(QString) definition and what is it doing?
All you have to do is:

// In List class
void List::get_movie(QString m)
{
    ui->label->setText(m);
}

RootLearner

I understand how we update the value in the ui. But I want to assign that value to a new variable in my second window. As in, I want to pass that username in a database and run a query. I cannot get that movie name under a variable. That is my main problem. I read documentations and also searched other projects. I just do not tend to get the idea of how I can assign the value into a new variable.

jsulm

@RootLearner Can you please explain what variable in what second window?
Is this second window the List class?
If so then its dead easy:

// In List class
void List::get_movie(QString m)
{
    a = m; // I assume a was defined as class member, but could also be a local variable
    ui->label->setText(m);
}

RootLearner

@jsulm Okay, I understood this. But I want to know how I am going to call this slot?
My lists.cpp is:

#include "lists.h"
#include "ui_lists.h"

lists::lists(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::lists)
{
    ui->setupUi(this);
    QString a;
//I should be calling the slot here??? If yes, how?
    qDebug()<<a;//just an example
}

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

void lists::get_movie(QString m)
{
    a = m; // I
    ui->label->setText(m);
}

This says a is an undeclared identifier. How do I call this slot and where?
While calling, will it not ask for variable 'm'?

KroMignon

@RootLearner said in Slots in the second window?:

Okay, I understood this. But I want to know how I am going to call this slot?

Please, start to learn C++ basics:

what are classes
variable scope

If you define a local variable in a function, this variable is local to this function and can not be used in another function.

jsulm

@RootLearner As @KroMignon suggested: learn C++ first.
You declared a as local variable in lists constructor, so it only exists as long as this constructor is executed.
Declare a as class member...

And why do you want to call the slot? Slot is called automatically as soon as the signal is emitted.

RootLearner

@KroMignon It was dumb of me to not recognize it as a local variable. I didn't see I am actually declaring it in the constructor. I was thinking if the variable declared will have global scope. I messed up my concepts. Thank you for highlighting it.

RootLearner

@jsulm I assumed I was making it a class member by declaring it in the constructor. And I actually didn't know slots gets called automatically as soon as the signal is emitted. I only worked with 'onButtonClicked()' as a slot and it worked when I clicked the button. So, I assumed every slots will be required to be called by doing something specifically. Thank you for clearing out my misconception. I got the concept and now, I can apply it in my project!

RootLearner

@jsulm @KroMignon

#include "movielist.h"
#include "ui_movielist.h"
#include <QSqlDatabase>
#include <QSqlError>
#include <QSqlQueryModel>
#include <QSqlQuery>
#include <QDebug>
#include <QSqlRecord>
#include <QMessageBox>
#include "movie.h"

Movielist::Movielist(QWidget *parent) : QDialog(parent),
                                        ui(new Ui::Movielist)
{
    ui->setupUi(this);
    QSqlDatabase myfile;
    myfile = QSqlDatabase::addDatabase("QSQLITE");
    myfile.setDatabaseName("C:/Users/user/Documents/New folder/qtcode/movie.db");
    if (!myfile.open())
    {
        qDebug() << ("Failed to open the database");
    }
    else
    {
        qDebug() << ("Connected");
    }
    QSqlQueryModel *model = new QSqlQueryModel();
    QSqlQuery qry;

    
}

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

void Movielist::on_tableView_activated(const QModelIndex &index)
{
    movie m;
    int c = index.column();
    QString temp = ui->tableView->model()->data(index).toString();
    qDebug() << temp;
    m.setModal(true);
    hide();
    m.exec();
}

void Movielist::receive(int a)
{

    qDebug()<<"opening movielist";

    switch (a)
    {
    case 0:
    {
        qDebug()<<"case 0";
        QSqlQueryModel *model = new QSqlQueryModel();
        QSqlQuery qry;
        qry.prepare("select Name, Date, Ratings, Genre from movie order by Ratings DESC");
       qDebug()<<"Case 0 ko query";
        if (qry.exec())
        {
            model->setQuery(qry);
            ui->label_2->setText("Top Rated Movies");
            ui->tableView->setModel(model);
            ui->tableView->resizeColumnsToContents();
            qDebug()<<"case 0 query executed";
        }
        break;
    }
    case 1:
    {
        QSqlQueryModel *model1 = new QSqlQueryModel();
        QSqlQuery qry1;
        qry1.prepare("select Name, Date, Ratings, Genre from movie where Genre = 'Romantic' order by Ratings DESC ");
        if (qry1.exec())
        {
            model1->setQuery(qry1);
            ui->label_2->setText("Top Romantic Movies");
            ui->tableView->setModel(model1);
            ui->tableView->resizeColumnsToContents();
        }
        break;
    }
    }
}

When receive slot is called, the ui is not updated but when I close the window, the qDebug in "opening movielist" and case 0 is run. How do I solve this? I need it to update the ui as per the integer passed via signals.

KroMignon

@RootLearner said in Slots in the second window?:

When receive slot is called, the ui is not updated but when I close the window, the qDebug in "opening movielist" and case 0 is run. How do I solve this? I need it to update the ui as per the integer passed via signals.

For me it looks like there is a forever loop which locks the thread event loop.
The emitted signals are stored in event loop, but as the thread is lock in a forever loop, the associated slots are called when forever loop ends and event loop is running.

What are you doing in movie class?