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.