QFile as an argument of a function?

[Stanfillirenfro]

Here is the idea:
I want to modofy a text document in different ways. Coloring it, changing color, resizing it... For that, I want to carry out each operation in a single window. So I want to create a function which will be responsible of opening the text document and preparing it before each above mentioned operation starts. For example, the gap between lines should be removed... In order to avoid opening the same file and proceding the preperation every time, I have decided to perform this step in a seperate window and just to call the function everytime I have to perform an operation, without rewriting the code again. That is the idea.
The real problem is to find and argument for the same function in another window when this function is called. That is the problem I have at the line 10 of second class.cpp

Any help would be welcome.

[wysota]

Ok but so far you only seem to have a QLineEdit and no text document. Assuming the line edit holds the path to a file containing the document, you should start by opening the file and reading the document from it.

[Stanfillirenfro]

You are wright Wysota!
Also, that is what I've done in the first class (first class.cpp, line 13). I mean, I've opened the document here. Should I also do that in the second class? If yes, it is what I wanted to avoid.

[Santosh Reddy]

Do this

QStringList Heritage::operation1(QString fileName)
{
    QStringList list;
    QFile file1(fileName);
    //pupolate list
    return list;
}
 
void ChildWindow::operation2(Heritage &aFile, QStringList &list)
{
    list = aFile.operation1(m_openFile->text());
}

QStringList Heritage::operation1(QString fileName)
{
    QStringList list;
    QFile file1(fileName);
    //pupolate list
    return list;
}

void ChildWindow::operation2(Heritage &aFile, QStringList &list)
{
    list = aFile.operation1(m_openFile->text());
}

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[Stanfillirenfro]

Hi Reddy!

It is difficult and complicate, since in QFile file1(m_openFile->text()), I am showing the path to the file to be used. In the decalration of the function, we have QString fileName, which will not be used in this case. Moreover, when I am testing if the file can be opened (if(!file1.open(QIODevice::ReadOnly)), with the return after the line of QMessageBox, I have the following error: "error : return-statement with no value, in function returning 'QStringList'"

Questions:
1- How to indicated the path to the file to be used in the declaration of the function in the heather file?
2- How to overcome the problem leading to the error message?
3- How to sole the entire problem?

Many thanks!

I have the following modified code:

first class.h

#ifndef DEF_HERITAGE
    #define DEF_HERITAGE
 
    #include <QtGui>
 
 
    class Heritage: public QMainWindow
    {
    Q_OBJECT
 
    public:
    explicit Heritage(QWidget *parent = 0);
    virtual ~Heritage();
 
    public slots:
    QStringList operation1(QString fileName);
 
    private:
    QLineEdit *m_openFile;    
 
 
    };

#ifndef DEF_HERITAGE
    #define DEF_HERITAGE
     
    #include <QtGui>
     
     
    class Heritage: public QMainWindow
    {
    Q_OBJECT
     
    public:
    explicit Heritage(QWidget *parent = 0);
    virtual ~Heritage();
     
    public slots:
    QStringList operation1(QString fileName);
     
    private:
    QLineEdit *m_openFile;    
     
     
    };

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First class.cpp

#include "Heritage.h"
    #include "ChildWindow.h"
 
    Heritage::Heritage(QWidget *parent)
    {
    m_openFile = new QLineEdit;
    setWindowTitle("Heritage");
    setCentralWidget(centralWidget);
    }
 
    QStringList Heritage::operation1(QString fileName)
    {
 
    QFile file1(m_openFile->text());
QStringList list;
    if(!file1.open(QIODevice::ReadOnly))
    {
        QMessageBox::critical(m_openFile, "Warning", "Open a file please");
        return;
    }
    ....
   return list;
    }

#include "Heritage.h"
    #include "ChildWindow.h"
     
    Heritage::Heritage(QWidget *parent)
    {
    m_openFile = new QLineEdit;
    setWindowTitle("Heritage");
    setCentralWidget(centralWidget);
    }
     
    QStringList Heritage::operation1(QString fileName)
    {
    
    QFile file1(m_openFile->text());
QStringList list;
    if(!file1.open(QIODevice::ReadOnly))
    {
        QMessageBox::critical(m_openFile, "Warning", "Open a file please");
        return;
    }
    ....
   return list;
    }

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Second class.h

#ifndef DEF_CHILDWINDOW
    #define DEF_CHILDWINDOW
 
    #include<QtGui>
    #include"Heritage"
 
    class ChildWindow: public QWidget
    {
    Q_OBJECT
 
    public:
    explicit ChildWindow(QWidget *parent = 0);
    virtual ~ChildWindow();
 
    public slots:
    void operation2(Heritage &aFile, QStringList &list);
 
    private:
 
    };
 
    #endif // CHILDWINDOW_H

#ifndef DEF_CHILDWINDOW
    #define DEF_CHILDWINDOW
     
    #include<QtGui>
    #include"Heritage"
     
    class ChildWindow: public QWidget
    {
    Q_OBJECT
     
    public:
    explicit ChildWindow(QWidget *parent = 0);
    virtual ~ChildWindow();
     
    public slots:
    void operation2(Heritage &aFile, QStringList &list);
     
    private:
     
    };
     
    #endif // CHILDWINDOW_H

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Second class.cpp

#include "ChildWindow.h"
    #include "Heritage.h"
 
    ChildWindow::ChildWindow(QWidget *parent)
    : QWidget(parent)
    {
    }
    void ChildWindow::operation2(Heritage &aFile, QStringList &list)
    {
    list = aFile.operation1(m_openFile->text());
    }
 
 
    ChildWindow::~ChildWindow()
    {
    ;
    }

#include "ChildWindow.h"
    #include "Heritage.h"
     
    ChildWindow::ChildWindow(QWidget *parent)
    : QWidget(parent)
    {
    }
    void ChildWindow::operation2(Heritage &aFile, QStringList &list)
    {
    list = aFile.operation1(m_openFile->text());
    }
     
     
    ChildWindow::~ChildWindow()
    {
    ;
    }

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[Santosh Reddy]

just return empty list

if(!file1.open(QIODevice::ReadOnly))
    {
        QMessageBox::critical(m_openFile, "Warning", "Open a file please");
        return list;
    }

if(!file1.open(QIODevice::ReadOnly))
    {
        QMessageBox::critical(m_openFile, "Warning", "Open a file please");
        return list;
    }

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[Stanfillirenfro]

Many thanks Reddy for yor help!
The error message has dissapear now, but another problem remains. Please have a look on first class.cpp, line 11 in my previous post. fileName is not used at all. If I delete it, it will not compile.
Do you have an idea how to solve the problem?

[Santosh Reddy]

If filename is not used, how does ChildWindow tell Heritage which file to open?

[Stanfillirenfro]

Maybe I was not clear.
In my code, at the level of first class.cpp line 11, we have:

QStringList Heritage::operation1(QString fileName)

QStringList Heritage::operation1(QString fileName)

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On the line 14, we have:

QFile file1(m_openFile->text());

QFile file1(m_openFile->text());

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m_openFile->text() replaces what you called in your code fileName, and what I've added here too. But the variable "fileName" is not used. It was my problem.
To answer to your qestion, according to me, ChildWindow shows the path to the file to be opned to Heritage with the expression: m_openFile->text().
Could you please clarify this situation? I would be grateful to you.

[Santosh Reddy]

I think you are missing some basic concepts.

you need to open "filename", not "m_openFile->text()",

[Stanfillirenfro]

Many thanks Reddy!
It is working now.
One more time, many thanks for your advices and help.