QObject::connect problem with argument list

sheehan1234

I'm to get the name of a file from the user's selection from a QFileSystemModel using a QTreeView. I get a compile error saying it couldn't convert the argument list when I do this

@QString localFileName = "";
QObject::connect(button, SIGNAL(clicked()), &localFileName, SLOT(append((model->data(tree->currentIndex(), Qt::DisplayRole)).toString())));@

I know the last argument is messy, but its what I thought would work to get the file name only when the user clicks the button

Eddy

In the slot you cannot have more arguments than the signal you're connecting with.
Furthermore you should only put types in there, not variables.

xeroblast

you could try :

@
private:
QString filename;
@

@
myClass::myClass () {
connect(button, SIGNAL(clicked()), this, SLOT(appendFilename()));
}

myClass::appendFilename() {
filename = model->data(tree->currentIndex(), Qt::DisplayRole).toString();
}
@

Kxyu

It's a sad thing that you can't connect a 0-argument signal with a non-0-argument slot with some specified in connect parameters, but it's true. So the only way to do that is to create a 0-argument slot and 1-argument signal, and connect them like clicked()->newSlot(), newSignal(arg)->append(arg), where the newSignal is emmited from newSlot.

andre

Well, many cases can be served by using QSignalMapper, and otherwise you can wait for Qt 5 that will support using a lambda function instead.

Kxyu

Oh, didn't know that! QSignalMapper appears to be perfect for this case.

sheehan1234

It looks really useful, but I'm hoping to see if I can get this code to work before I erase all of it. The only problem now is a runtime error that says this in the command window:

QObject::connect: No such slot QWidget::appendFileName()

I do have appendFileName() declared a public slot and i have written the code that I want for the function itself

sheehan1234

Does anyone know why I'm getting that error?

Kxyu

Code please. I have a guess, but code first

sheehan1234

Public Declarations:
@QFileSystemModel model;
QTreeView tree;
QString file;@

The subroutine:
@void MyWidget::appendFileName()
{
file.append((model.data(tree.currentIndex(), Qt::DisplayRole)).toString());
fileAttained = true;
}@

In the main:
@
model.setRootPath(QDir::currentPath());
tree.setModel(&model);
QWidget *wid = new QWidget;
button.setText("Select File");

layout.addWidget(&tree);
layout.addWidget(&button);

wid->setLayout(&layout);
wid->setFixedSize(1100, 500);
wid->show();

QObject::connect(&button, SIGNAL(clicked()), this, SLOT(appendFileName()));@

Kxyu

I don't get it. So you define a class MyWidget, then instantiate just simple Widget object and after all use this pointer in main(). Altogether this makes no sense.

sheehan1234

that's my mistake, the main has a function call @widget.getFile();@ which is here:
@void MyWidget::getFile()
{
model.setRootPath(QDir::currentPath());
tree.setModel(&model);
tree.setColumnWidth(0, 500);
tree.resize(1000, 300);
QWidget *wid = new QWidget;
button.setText("Select File");

layout.addWidget(&tree);
layout.addWidget(&button);

wid->setLayout(&layout);
wid->setFixedSize(1100, 500);
wid->show();

QObject::connect(&button, SIGNAL(clicked()), this, SLOT(appendFileName()));

}@

Maybe this makes a bit more sense, I appreciate you helping. What was your guess?

goetz

Did you declare appendFileName() as a slot in your class header?

@
class MyWidget {
// ....

protected slots:
void appendFileName();

};
@

sheehan1234

yes sir I did

goetz

Then show us the complete code, please.

sheehan1234

@#include <QtGui>
#include <fstream>
#include <iostream>

using namespace std;

class MyWidget : public QWidget
{

public:
MyWidget();
float currX1, currX2, currY1, currY2, nextX1, nextX2, nextY1, nextY2;
float points[105][105];
QString file;
int numCols;
int numRows;
QFileSystemModel model;
QTreeView tree;
QVBoxLayout layout;
QPushButton button;
bool fileAttained;
void getFile();

protected slots:
void appendFileName();

protected:
void paintEvent(QPaintEvent *);

};

MyWidget::MyWidget()
{
QPalette palette(MyWidget::palette());
palette.setColor(backgroundRole(), Qt::white);
setPalette(palette);

}

void MyWidget::paintEvent(QPaintEvent *)
{
// omitted
}
void MyWidget::appendFileName()
{
file.append((model.data(tree.currentIndex(), Qt::DisplayRole)).toString());
fileAttained = true;
}
void MyWidget::getFile()
{
model.setRootPath(QDir::currentPath());
tree.setModel(&model);
tree.setColumnWidth(0, 500);
tree.resize(1000, 300);
QWidget *wid = new QWidget;
button.setText("Select File");

layout.addWidget(&tree);
layout.addWidget(&button);

wid->setLayout(&layout);
wid->setFixedSize(1100, 500);
wid->show();

QObject::connect(&button, SIGNAL(clicked()), this, SLOT(appendFileName()));
QObject::connect(&button, SIGNAL(clicked()), wid, SLOT(close()));

}
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MyWidget widget;
widget.getFile();

    // omitted

return app.exec();
}
@

I have code commented out/ omitted from the post that does the second part of the program which is what relies on getting the name of the file that the user chooses

giesbert

You missed the Q_OBJECT macro in your header file opf MyWidget:

@
class MyWidget : public QWidget
{
// this is missing
Q_OBJECT;
public:
MyWidget();
float currX1, currX2, currY1, currY2, nextX1, nextX2, nextY1, nextY2;
float points[105][105];

protected slots:
void appendFileName();

protected:
void paintEvent(QPaintEvent *);
};
@

sheehan1234

thank you, I had tried that and gotten errors so I thought it was wrong. so i tried again, got link errors, and I included "main.moc". Now there aren't link errors, but a the moc file has errors that I don't know how to fix. There are about 10 of them, heres the first to give you an example
@1>.\GeneratedFiles\Release\main.moc(42) : error C2653: 'MyWidget' : is not a class or namespace name@

I can copy the moc file too if you need it

Eddy

Looks like you didn't include mywidget.h in your main.

giesbert

Split up the class definition into a header file, and don't put definition and implemenation together in the cpp file.
then it should work.

Or include main.moc at the end of the file.