C++ Qt4: Add slot with QObject implementation - c++

Question

I'm fairly new to Qt in general, and I would like to use some degree of reflection in writing a generic method for printing lists of objects.
I'm currently trying to hook up to the ui like so:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <algorithm>
#include <QStringListModel>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
...
connect(ui->print_books_btn, SIGNAL(released()), this, SLOT(PrintList(BookList)));
connect(ui->print_clients_btn, SIGNAL(released()), this, SLOT(PrintList(ClientList)));
}
...
void MainWindow::PrintList(QList<QMetaObject*> list)
{
list.first()->className();
}
My relevant header files look like so:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
...
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();
...
private:
Ui::MainWindow *ui;
QList<Book*> BookList;
QList<Client*> ClientList;
private slots:
...
void PrintList(QList<QMetaObject*> list);
};
#endif // MAINWINDOW_H
I believe I've set everything up with regards to the Q_OBJECT macro in the header files:
...
class Book : public QObject
{
Q_OBJECT
public:
Book();
...
}
Everything compiles without error, though when running I get this in the console:
QObject::connect: No such slot MainWindow::PrintList(BookList) in ..\LibraryManager\mainwindow.cpp:18
QObject::connect: (sender name: 'print_books_btn')
QObject::connect: (receiver name: 'MainWindow')
QObject::connect: No such slot MainWindow::PrintList(ClientList) in ..\LibraryManager\mainwindow.cpp:19
QObject::connect: (sender name: 'print_clients_btn')
QObject::connect: (receiver name: 'MainWindow')
Is it possible to work it this way?
Thanks!
UPDATE
I think its QMetaObject that I actually want to be using - so I can do list.first()->className() etc. Edited above ^
UPDATE 2
Required to be using Qt4.

Answer 1

released() signals of QPushButtons would not send any parameters like QMetaObject* as you like to your slots SLOT(PrintList(...))
so your implementation is wrong,
you should think another way for example you take the released() [or clicked()] signals of QPushButtons and connect them to another slot in your class like buttonsClicked() then in the implementation of buttonsClicked() slot you should manually emit a signal with parameters like booklist or clientlist as you like to be received in the other slot PrintList(QMetaObject*)
this is how signals and slots are working in Qt. Slots only receive parameters emitted by signal not any other parameters.

Answer 2

I think you should connect both signals to SLOT(PrintList(QList<QObject*>))).
In the PrintList(QList<QObject*> list) you can use dynamic_cast to check what type it is (BookList or ClientList) then you can print what you want depend on its type.

Answer 3

In Qt5, you can use lambda functions in the QObject::connect method to pass a parameter to your slot:
connect(ui->print_books_btn, &QPushButton::clicked, [=] { PrintList(BookList); });
You can also use the QSignalMapper class to do the same thing in Qt4 (see the doc). Or, you can create two specific slots:
connect(ui->print_books_btn, SIGNAL(released()), this, SLOT(printBookList));
void MainWindow::printBookList()
{
printList(bookList);
}
The last solution is maybe the best way: it's explicit and more readable.