Using a pointer to a QTextStream & QFile

iwasapenguin · 04-16-2008, 04:30 PM

I've tried the QT forums for this but the KDE development section
looks like a ghost town.

The problem is that I'm attempting to have a class that holds a
QFile, QTextStream and KTextEdit and will save the file when
a button is pressed. These are in a QPtrList and displayed on
a QTabWidget.

The trouble is though that I can't compile the code without the QFile
being declared in the class constructor but it also needs to be accessed
by a slot to save the file and the same runs for the QTextStream.

I attempted to use pointers to fix this but the line:

Code:

streamPtr->operator<<( filePtr )

caused a seg fault (though I didn't expect much of it).

Would anybody know how to either get the pointer method to work
or better approach?

graemef · 04-16-2008, 06:37 PM

This may not be a ghost town but do we have the right sign posts?

I'm not certain if I understand the problem but are you struggling with compile errors about the redeclaration of QFile?

If so you will need to first check your header guards, next if all of those are in place correctly do a forward declaration of your QFile object.

Maybe posting the relevant code with the error will help.

iwasapenguin · 04-16-2008, 10:52 PM

This is why newbies (i.e. me) shouldn't try to code semi-ide's...

From bridgetextedit.h

Code:

class bridgeTextEdit : public QObject {
Q_OBJECT
public:
	bridgeTextEdit( QTabWidget *parent, QDomElement fileElement, bridgeMainWindow *window  );
	virtual ~bridgeTextEdit();

	QVBox *controll;
	QLabel *label;
	KTextEdit *editField;

public slots:
	void slotSaveFile();
	void slotSaveFileAs();

private:
	QTextStream *streamPtr;
};

from bridgetextedit.cpp

Code:

bridgeTextEdit::bridgeTextEdit( QTabWidget *parent, QDomElement fileElement, bridgeMainWindow *window )
	: QObject()
{

	//initialise the gui
	controll = new QVBox( parent );

	label = new QLabel( controll );
	label->setText( fileElement.attribute("descrip") );

	editField = new KTextEdit( controll );
	editField->setMinimumHeight( 600 );
	editField->setMinimumWidth( 800 );

	parent->addTab( controll, fileElement.attribute("url"));

	//all file realted isuses below
	QFile file( fileElement.attribute("url") );
	if ( !file.open( IO_ReadWrite ) )
		goto error;
	else{
		 QTextStream stream( &file );
		 editField->setText( stream.read() );

		 streamPtr = &stream;
	}

...

void bridgeTextEdit::slotSaveFile()
{
        streamPtr->operator<<( file );
	editField->setModified( false );
}

Or something like that. I ripped out the offending code so that
I could work on other parts of it in the mean time.

Mara · 04-18-2008, 03:55 PM

I see two possible things: first one is the set of includes you have. You don't show them, so it's hard to say that's the reason. Also, I would be careful with declaring QT-based classes as local variables:

Code:

QFile file( fileElement.attribute("url") );

Instead, I'd rather write

Code:

QFile *file = new QFile( fileElement.attribute("url") );

If it doesn't help, show us the exact compilation error you get.

iwasapenguin · 04-20-2008, 12:21 AM

here's the output from make when I try to have a function that uses pointers to streams and
files...

g++ -c bridgetextedit.cpp -o bridgetextedit.o -I/usr/lib/qt-3.3/include -I/usr/include/kde -g -Wall
...
bridgetextedit.cpp: In member function ‘void bridgeTextEdit::slotSaveFile()’:
bridgetextedit.cpp:63: error: no match for ‘operator<<’ in ‘((bridgeTextEdit*)this)->bridgeTextEdit::streamPtr << QTextEdit::text() const()’

... And the matching code...

(From the class declaration)

Code:

class bridgeTextEdit : public QObject {
Q_OBJECT
public:
	bridgeTextEdit( QTabWidget *parent, QDomElement fileElement, bridgeMainWindow *window  );
	virtual ~bridgeTextEdit();

	QVBox *controll;
	QLabel *label;
	KTextEdit *editField;

public slots:
	void slotSaveFile();
	void slotSaveFileAs();

private:
	QFile *filePtr;
	QTextStream *streamPtr;
};

(from the constructor)

Code:

filePtr = new QFile( fileElement.attribute("url") );
	if ( !file->open( IO_ReadWrite ) )
		goto error;
	else{
		 streamPtr  = new QFile( file );
		 editField->setText( stream->read() );
	}

(and from the save function)

Code:

void bridgeTextEdit::slotSaveFile()
{

	streamPtr << editField->text();
	editField->setModified( false );
}

Mara · 04-21-2008, 02:09 PM

This doesn't compile:

Code:

    QTextStream *ts = new QTextStream();
    ts << "blah";

But this one does:

Code:

    QTextStream *ts = new QTextStream();
    *ts << "blah";

It's exactly the same in your case.