Save object to a file

SGaist

Hi and welcome to devnet,

If you want to use streams with your custom objects, you have to define the QTextStream's operator for them otherwise QTextStream won't be able to serialize them.

Dmon

thanks I added this function to define toString

QString Film::toString()
{
return m_title + " " + m_duration + " " + m_director + " " + m_releaseDate.toString();
}

now I am getting error:
debug/filminput.o:C:\Unisa\COS3711\assignments\Ass1Q1-build-desktop/../Ass1Q1/filminput.cpp:63: undefined reference to `FilmInput::saveFilm(Film&)'
collect2: ld returned 1 exit status
mingw32-make[1]: *** [debug\Ass1Q1.exe] Error 1
mingw32-make: *** [debug] Error 2
The process "C:/Qt/2010.04/mingw/bin/mingw32-make.exe" exited with code %2.
Error while building project Ass1Q1 (target: Desktop)
When executing build step 'Make'

SGaist

School work ?

It seems the compiler doesn't know about saveFilm

Dmon

Yes it's an assignment I'm doing. I don't understand how it doesn't see it because saveFilm is a function in class FilmWriter which is included in class definition for class FilmInput which is has a function which calls saveFilm.

SGaist

Without the code it's difficult to comment

Dmon

@#ifndef FILM_H
#define FILM_H

#include <QWidget>
#include <QString>
#include <QDate>

class Film:public QWidget{
public:
Film(QString t,int dur,QString dir,QDate r);
Film();
void setTitle(QString t);
void setDuration(int dur);
void setDirector(QString dir);
void setReleaseDate(QDate r);
QString getTitle() const;
int getDuration() const;
QString getDirector() const;
QDate getReleaseDate() const;
QString toString();

private:
QString m_title;
int m_duration;
QString m_director;
QDate m_releaseDate;

};

#endif // FILM_H

#ifndef FILMWRITER_H
#define FILMWRITER_H
#include "Film.h"
#include <QtGui>
#include <QFile>

class FilmWriter: public Film{

public:
void saveFilm(Film& f);

};
#endif // FILMWRITER_H

#ifndef FILMINPUT_H
#define FILMINPUT_H

#include <QMainWindow>
#include "Film.h"
#include "FilmWriter.h"
#include <QLabel>
#include <QTextEdit>
#include <QPushButton>

namespace Ui {
class FilmInput;
}

class FilmInput : public QMainWindow
{
Q_OBJECT

public:
explicit FilmInput(QWidget parent = 0);
~FilmInput();
void obtainFilmData(Film& f);
void saveFilm(Film& f);
public slots:
void getFilm();
private:
Ui::FilmInput ui;
//widgets
QMainWindow window;
QLabel infoLabel;
QLabel* titleLabel;
QLabel* durationLabel;
QLabel* directorLabel;
QLabel* relDateLabel;
QTextEdit* titleEdit;
QTextEdit* durationEdit;
QTextEdit* directorEdit;
QTextEdit* relDateEdit;
QPushButton* saveBtn;
QPushButton* cancelBtn;
Film f;
//sets up gui and connects signals and slots
void setUpGui();
};

#endif // FILMINPUT_H

#include "Film.h"
#include <QDate>
#include <QString>

Film::Film(QString t,int dur,QString dir,QDate r):m_title(t),m_duration(dur),m_director(dir),m_releaseDate(r){

}

Film::Film(){
}

void Film::setTitle(QString t){
m_title = t;
}

void Film::setDuration(int dur){
m_duration = dur;
}

void Film::setDirector(QString dir){
m_director = dir;
}

void Film::setReleaseDate(QDate r){
m_releaseDate = r;
}

QString Film::getTitle() const{
return QString("%1").arg(m_title);
}

int Film::getDuration() const{
return m_duration;
}
QString Film::getDirector() const{
return QString("%1").arg(m_director);
}
QDate Film::getReleaseDate() const{
return m_releaseDate;
}
QString Film::toString()
{
return m_title + " " + m_duration + " " + m_director + " " + m_releaseDate.toString();
}

#include "FilmWriter.h"
#include <QtGui>
#include <QFileDialog>
#include <QFile>
#include <QMessageBox>
#include <QObject>
#include <QTextStream>

void FilmWriter::saveFilm(Film& f){
QString fileName = QFileDialog::getSaveFileName(this,("Save File"));
if (fileName != "") {
QFile file(fileName);
if (!file.open(QIODevice::WriteOnly)) {
QMessageBox::critical(this, ("Error"),("Could not open file"));// error message
} else {
QTextStream stream(&file);
stream << f.toString();
stream.flush();
file.close();
}
}

}

#include "filminput.h"
#include "ui_filminput.h"
#include <QtGui>
#include "Film.h"
#include "FilmWriter.h"
#include <QTextEdit>
#include <QDate>
#include <QString>

FilmInput::FilmInput(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::FilmInput)
{
ui->setupUi(this);
setUpGui();
}

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

void FilmInput::setUpGui(){
//initialise widgets
infoLabel = new QLabel("Please enter film data which will be saved to a file",this);
titleLabel = new QLabel("Film Title",this);
durationLabel = new QLabel("Film Duration",this);
directorLabel = new QLabel("Film Director",this);
relDateLabel = new QLabel("Film Release Date",this);
titleEdit = new QTextEdit(this);
durationEdit = new QTextEdit(this);
directorEdit = new QTextEdit(this);
relDateEdit = new QTextEdit(this);
saveBtn = new QPushButton("Save Film",this);
cancelBtn = new QPushButton("Cancel",this);
//set layout
QFormLayout* layout = new QFormLayout();
layout->addWidget(infoLabel);
layout->addWidget(titleLabel);
layout->addWidget(titleEdit);
layout->addWidget(durationLabel);
layout->addWidget(durationEdit);
layout->addWidget(directorLabel);
layout->addWidget(directorEdit);
layout->addWidget(relDateLabel);
layout->addWidget(relDateEdit);
layout->addWidget(saveBtn);
layout->addWidget(cancelBtn);

this->ui->widget->setLayout(layout);
this->setWindowTitle("Film Archive");
connect(saveBtn,SIGNAL(clicked()),this, SLOT(getFilm()));
connect(cancelBtn,SIGNAL(clicked()),this,SLOT(close()));

}

void FilmInput::getFilm(){
Film f1(titleEdit->toPlainText(),durationEdit->toPlainText().toInt() ,directorEdit->toPlainText(),
QDate::fromString(relDateEdit->toPlainText(),"dd/MM/YYYY"));;
obtainFilmData(f1);
}

void FilmInput::obtainFilmData(Film &f){
saveFilm(f);
}

#include <QtGui/QApplication>
#include "filminput.h"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);

FilmInput w;
w.show();

return a.exec&#40;&#41;;

}
@

SGaist

saveFilm is not a member of FilmInput.

Besides that, please, got through the examples and the documentation of Qt, that would be beneficial to you.

I don't want to sound rude but what you wrote here will not do for an assignment.

Why does Film inherit QWidget ?
Why does FilmWriter inherit Film if it's only function is to write a Film given as a parameter ?
Why do you use a UI file if you create your interface by hand anyway ?

Dmon

I thought that FilmWriter would need to inherit Film in order to create an object of type Film. Film inheriting QWidget is a mistake as it is left over from the question which was one class called film inheriting QWidget which I have to break up into 3 classes and then add functionality. Also the UI file was created automatically for me with Qt creator. I will look up some info on interfaces. So the question is to have the saveFilm function in the filmWriter class, how do I get it to work like that rather than making saveFilm a member of FilmInput and removing the FilmWriter class?

SGaist

No it doesn't, as long as it knows how to use Film.

For the rest it's essentially doc reading

Dmon

if I take out #include "Film.h" in FilmWriter there is a problem with the FilmWriter class, if I then take out : public Film there is a problem with the func saveFilm because it's parameter is of type Film. So how do I make it know how to use Film?

SGaist

This is C/C++ basic knowledge. Without the header file how would your class know anything about Film ?

What problem would it be ?

Dmon

well it wouldn't know about Film without the header file. Are you saying that it doesn't need to be a child of Film but just include the header?

SGaist

Yes, it's exactly what I'm saying

Dmon

Ok great. But now after the changes I am still getting the same error :-?
:: error: collect2: ld returned 1 exit status

SGaist

If you are talking about the saveFilm problem and the message didn't changed, then saveFilm is still not a member of FilmInput.

Isn't it a member of FilmWriter ?

Dmon

Yes and I don't want it to be a member of FilmInput, I want it to be member of FilmWriter only and somehow (I don't know how) be called in FilmInput. I thought if I included the FilmWriter header it would work, but obviously I must do something else.

SGaist

FilmWriter is a class, how do you call a function from a class ?

Dmon

You create an object and call the function with the object. That's it! Ok so now you have helped me to get rid of that error, thanks a lot. Another question, when I click on the save film button which invokes saveFilm the program crashes, should I start a new thread because this is a new question or can you still help me on this one?

SGaist

Run your application through the debugger, it will tell you where the crash occurs

Dmon

I got this: The inferior stopped because it received a signal from the operating system
signal name: SIGSEGV
Signal meaning: Segmentation fault
then it is pointing to line 2185 in qglobal.h
inline QFlags operator&(Enum f) const { QFlags g; g.i = i & f; return g; }