Need help passing a variable to another Form (Signals/Slots)
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@jsulm I have found a little mistake. I accidentally assigned the emit call to the signal instead of the slot. After correcting this I tried connecting 2 instances of my class Option inside the MainWindow class which worked (I think). I still can't see an instance of Option outside the MainWindow class.
functions.h
#include <QtSql> #include <QSqlDatabase> #include <QTableView> class Option: public QObject { Q_OBJECT private: QSqlDatabase db; int mode; public: QSqlDatabase get_db(){return this->db;} int get_mode(){return this->mode;} signals: void send_option(QSqlDatabase db, int mode); public slots: void set_up(QSqlDatabase db, int mode){ this->db = db; this->mode = mode; emit send_option(db, mode);} };mainwindow.h
//... class MainWindow : public QMainWindow { Q_OBJECT public: explicit MainWindow(QWidget *parent = nullptr); ~MainWindow(); private slots: void on_pushButton_connect_clicked(); void on_pushButton_create_pdf_clicked(); void on_pushButton_save_settings_clicked(); void on_pushButton_open_clicked(); private: Ui::MainWindow *ui; int create_pdf(); Dialog dialog; QSqlDatabase db; Option opt_main, testopt; //testopt was the test-instance i used };mainwindow.cpp
//... QObject::connect(&opt_main, &Option::send_option, &opt_dia, &Option::set_up); //opt_dia not declared in this scope //... void MainWindow::on_pushButton_open_clicked() { opt_main.send_option(db, 123); dialog.setModal(true); dialog.exec(); }dialog.h
//... #include "functions.h" namespace Ui { class Dialog; } class Dialog : public QDialog { Q_OBJECT public: explicit Dialog(QWidget *parent = nullptr); //QObject* x; Option opt_dia; ~Dialog(); private: Ui::Dialog *ui; void load_meta(); int mode; private slots: void on_pushButton_ok_clicked(); };dialog.cpp
//... void Dialog::on_pushButton_ok_clicked() { qDebug() << "mode: " + QString::number(opt_dia.get_mode()) + " - " + opt_dia.get_db().userName(); //testing the result }opt_dia cannot be found since it's not declared in this scope. If I use &Dialog::opt_dia it is found but the connection will fail to compile with the following error: Fehler: no matching member function for call to 'connect'
@SnuggleKat Why don't you simply define the slot inside Dialog class?
Exposing a member (opt_dia) as public to outside world is bad design. -
@SnuggleKat Why don't you simply define the slot inside Dialog class?
Exposing a member (opt_dia) as public to outside world is bad design.@jsulm said in Need help passing a variable to another Form (Signals/Slots):
@SnuggleKat Why don't you simply define the slot inside Dialog class?
Exposing a member (opt_dia) as public to outside world is bad design.I'm aware it's bad design. That's why I asked what'd be the best way to instantiate it.
Is it the right way to access the signal through opt_dia if I define the slot inside the Dialog class?
And what should the connect() look like now? -
@jsulm said in Need help passing a variable to another Form (Signals/Slots):
@SnuggleKat Why don't you simply define the slot inside Dialog class?
Exposing a member (opt_dia) as public to outside world is bad design.I'm aware it's bad design. That's why I asked what'd be the best way to instantiate it.
Is it the right way to access the signal through opt_dia if I define the slot inside the Dialog class?
And what should the connect() look like now?@SnuggleKat said in Need help passing a variable to another Form (Signals/Slots):
When I define the slot inside the Dialog class is it the right way to access the signal through opt_dia?
I don't understand this - what signal do you want to access from opt_dia?
Connect would be:connect(&opt_main, &Option::send_option, &dialog, &Dialog::set_up);Actually I don't see a need for signal/slot here as dialog is a member of MainWindow. set_up can be a normal method which you call like any other without emiting a signal:
dialog.set_up(...); -
@SnuggleKat said in Need help passing a variable to another Form (Signals/Slots):
When I define the slot inside the Dialog class is it the right way to access the signal through opt_dia?
I don't understand this - what signal do you want to access from opt_dia?
Connect would be:connect(&opt_main, &Option::send_option, &dialog, &Dialog::set_up);Actually I don't see a need for signal/slot here as dialog is a member of MainWindow. set_up can be a normal method which you call like any other without emiting a signal:
dialog.set_up(...);@jsulm Sorry, I meant to ask if ithis would be the right way of doing it:
public slots: void set_up(QSqlDatabase db, int mode){ this->db = db; this->mode = mode; emit opt_dia.send_option(db, mode);}Change the connect() method as suggestion but the values don't get passed over.
Same for adding dialog.set_up();
Should I make QSqlDatabase db and int mode static? -
@jsulm Sorry, I meant to ask if ithis would be the right way of doing it:
public slots: void set_up(QSqlDatabase db, int mode){ this->db = db; this->mode = mode; emit opt_dia.send_option(db, mode);}Change the connect() method as suggestion but the values don't get passed over.
Same for adding dialog.set_up();
Should I make QSqlDatabase db and int mode static?@SnuggleKat "Change the connect() method as suggestion but the values don't get passed over." - please show the code.
"Should I make QSqlDatabase db and int mode static?" - please don't! Static variables are bad design in most cases. -
@SnuggleKat "Change the connect() method as suggestion but the values don't get passed over." - please show the code.
"Should I make QSqlDatabase db and int mode static?" - please don't! Static variables are bad design in most cases.@jsulm said in Need help passing a variable to another Form (Signals/Slots):
@SnuggleKat "Change the connect() method as suggestion but the values don't get passed over." - please show the code.
"Should I make QSqlDatabase db and int mode static?" - please don't! Static variables are bad design in most cases.That's what I thought.
void MainWindow::on_pushButton_open_clicked() { opt_main.send_option(db, 123); QObject::connect(&opt_main, &Option::send_option, &dialog, &Dialog::set_up); dialog.set_up(db, 123); //also tried this which didn't help either dialog.setModal(true); dialog.exec(); } -
@jsulm said in Need help passing a variable to another Form (Signals/Slots):
@SnuggleKat "Change the connect() method as suggestion but the values don't get passed over." - please show the code.
"Should I make QSqlDatabase db and int mode static?" - please don't! Static variables are bad design in most cases.That's what I thought.
void MainWindow::on_pushButton_open_clicked() { opt_main.send_option(db, 123); QObject::connect(&opt_main, &Option::send_option, &dialog, &Dialog::set_up); dialog.set_up(db, 123); //also tried this which didn't help either dialog.setModal(true); dialog.exec(); }@SnuggleKat I really don't get why you use signals slots here?
void MainWindow::on_pushButton_open_clicked() { dialog.set_up(db, 123); //also tried this which didn't help either dialog.setModal(true); dialog.exec(); }"//also tried this which didn't help either" - please show what dialog.set_up(db, 123) is doing.
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@SnuggleKat I really don't get why you use signals slots here?
void MainWindow::on_pushButton_open_clicked() { dialog.set_up(db, 123); //also tried this which didn't help either dialog.setModal(true); dialog.exec(); }"//also tried this which didn't help either" - please show what dialog.set_up(db, 123) is doing.
@jsulm
qDebug() shows me that it effectively does nothing. dialog.set_up() does not touch the object declared as opt_dia."mode: 12141696 - "12141696 seems to be a random value.
This is the qDebug() line:qDebug() << "mode: " + QString::number(opt_dia.get_mode()) + " - " + opt_dia.get_db().userName(); -
@jsulm
qDebug() shows me that it effectively does nothing. dialog.set_up() does not touch the object declared as opt_dia."mode: 12141696 - "12141696 seems to be a random value.
This is the qDebug() line:qDebug() << "mode: " + QString::number(opt_dia.get_mode()) + " - " + opt_dia.get_db().userName();@SnuggleKat Can you show the content of dialog.set_up(...)?
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@jsulm Do you mean this?
public slots: void set_up(QSqlDatabase db, int mode){ this->db = db; this->mode = mode; emit opt_dia.send_option(db, mode);}@SnuggleKat set_up(
public slots: void set_up(QSqlDatabase db, int mode){ this->db = db; this->mode = mode; opt_dia.set_up(db, mode); } -
I admit, I'm a little bit out of my field here, but can you simply reassign a
QSqlDatabasein that way?I usually pass a QSqlDatabase-pointer between classes.
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@SnuggleKat set_up(
public slots: void set_up(QSqlDatabase db, int mode){ this->db = db; this->mode = mode; opt_dia.set_up(db, mode); }@jsulm
Okay, it now works! Thank you.
I also hat to re-write a set_up() function inside the Dialog class.
I will clean up the way it's done by now and remember it for the next time
