How to access this variable Qt? - c++

Question

Sorry the question is going to be long. I dont know how to shorten this. I am new to Qt. With a little bit of experience in c++, I thought I should start with Qt to make my programs graphical. I chose a single user library management software as a personal project.
I made a book class to get and set the name, author and uid of the book. I then made a library class to manage a vector of books. It can add presently only add a book and get a book at a particular index.
So, the code so far works fine. But I then tried to add GUI.
In the mainwindow constructor, i just added two predefined books to the library class object. The main window has 3 Line-edits to show the name, author, and uid of each book. It has two buttons "next" to show the next Book and "previous" to show the previous book.
I wanted a feature to add the book. So, created File menu and added Add Book using the Design menu. I went to slot.
What i want is to create a second window to ask for the name, author and uid of the new book. The fact is my library class object contains the details of all the books. How do i access that object so as to call addBook() function to add the book.
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "library.h"
#include "dialog.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
library getLib();
private slots:
void on_next_clicked();
void on_previous_clicked();
void on_actionAdd_book_triggered();
private:
Ui::MainWindow *ui;
int currentIndex;
library l;
Dialog* d;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
book b;
b.setAuthor("Ruskin Bond");
b.setName("The Jungle Book");
b.setUid("123456789");
l.addBook(b);
b.setAuthor("Savi Sharma");
b.setName("This is not your story");
b.setUid("789456123");
l.addBook(b);
b = l.getBook(0);
ui->lineEdit->setText(QString::fromStdString(b.getName()));
ui->lineEdit_2->setText(QString::fromStdString (b.getAuthor()) );
ui->lineEdit_3->setText(QString::fromStdString(b.getUid()));
currentIndex = 0;
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_next_clicked()
{
++currentIndex;
if(currentIndex < l.numOfBooks())
{
book b;
b = l.getBook(currentIndex);
ui->lineEdit->setText(QString::fromStdString(b.getName()));
ui->lineEdit_2->setText(QString::fromStdString(b.getAuthor()));
ui->lineEdit_3->setText(QString::fromStdString(b.getUid()));
}
}
void MainWindow::on_previous_clicked()
{
--currentIndex;
if(currentIndex >= 0)
{
book b;
b = l.getBook(currentIndex);
ui->lineEdit->setText(QString::fromStdString(b.getName()));
ui->lineEdit_2->setText(QString::fromStdString(b.getAuthor()));
ui->lineEdit_3->setText(QString::fromStdString(b.getUid()));
}
}
void MainWindow::on_actionAdd_book_triggered()
{
d = new Dialog(this);
d->show();
}
Dialog.h
#ifndef DIALOG_H
#define DIALOG_H
#include <QDialog>
namespace Ui {
class Dialog;
}
class Dialog : public QDialog
{
Q_OBJECT
public:
explicit Dialog(QWidget *parent = 0);
~Dialog();
private slots:
void on_pushButton_clicked();
private:
Ui::Dialog *ui;
};
#endif // DIALOG_H
dialog.cpp
#include "dialog.h"
#include "ui_dialog.h"
#include <QMessageBox>
Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
}
Dialog::~Dialog()
{
delete ui;
}
void Dialog::on_pushButton_clicked()
{
QString temp = ui->lineEdit->text(),
temp_2 = ui->lineEdit_2->text(),
temp_3 = ui->lineEdit_3->text();
if(temp == "" || temp_2 == "" || temp_3 == "")
QMessageBox :: warning(this, "Warning!", "One of the lines is empty");
else
{
book b(temp.toStdString(), temp_2.toStdString(), temp_3.toStdString());
//how do i add the book?
}
}
This is what that appears:
Your answer

Answer 1

I hope the addBook in library class is to add the book into the list. You can create one connection which will pass the details of the book as follow from Dialog to Mainwindow:-
In Dialog class create one signal which will send the details of the book. For example in Dialog.h in class Dialog declare signal like this:-
signals:
void bookDetailsEntered(book b);
In Dialog.cpp emit this signal in on_pushButton_clicked():-
void Dialog::on_pushButton_clicked()
{
QString temp = ui->lineEdit->text(),
temp_2 = ui->lineEdit_2->text(),
temp_3 = ui->lineEdit_3->text();
if(temp == "" || temp_2 == "" || temp_3 == "")
QMessageBox :: warning(this, "Warning!", "One of the lines is
empty");
else
{
book b(temp.toStdString(), temp_2.toStdString(), temp_3.toStdString());
emit bookDetailsEntered(b);
}
}
Now in MainWindow.h declare one slot which will receive the details of the book like this:-
private slots:
void onBookDetailsEntered(book b);
and in MainWindow.cpp create connection from the signal in Dialog.h to the slot in Mainwindow like this:-
void MainWindow::on_actionAdd_book_triggered()
{
d = new Dialog(this);
connect(d,SIGNAL(bookDetailsEntered(book)),
this,SLOT(onBookDetailsEntered(book)));
// FYI, You can use Dialog here like Dialog d(in stack instead of heap).
// By this the d variable will get destroyed once the d is out of scope.
// Here you're creating the multiple instance of Dialog(each time when you show Dialog which will consume more memory)
}
void MainWindow::onBookDetailsEntered(book b)
{
library.addBook(b);
}
I hope i answered your question.

Answer 2

you need to show the dialog in your on_actionAdd_book_triggered(). i.e.
d->show();