variable or field 'newDataSlot' declared void {line 27 below}

'changed' was not declared in this scope {line 27 below}

The connection is defined in main

@ 1 #include <QtGui/QApplication>
2 #include "pass.h"

3 int main(int argc, char *argv[])
4 {
5 QApplication a(argc, argv);
6 pass w;
7 addNew child;

8 QObject::connect(&child, SIGNAL(dataChangedSignal(bool)), &w, SLOT(newDataSlot(bool)));

9 w.show();

10 return a.exec();
}@

I have the following definitions in pass.h

@11 public:
12 explicit pass(QWidget *parent = 0);
13 ~pass();
14 void readDataFile();
15 QString name;
16 QString user;
17 QString date;
18 QString spin;
19 QString fileName;
20 bool changed;

21 private slots:
22 void on_pushButtonQuit_clicked();
23 void on_comboBox_currentIndexChanged();23
24 void on_pushButtonNew_clicked();
25 void on_pushButtonShow_clicked();
26 void newDataSlot(bool);@

newDataSlot() is defined in passKeeper as

@27 void pass::newDataSlot(changed)
29 {
30 if (changed)
31 readDataFile();
32 }@

In addNew.h the following signals and slots have been defined:

@33 private slots:
34 void on_pushButtonAdd_clicked();
35 void on_pushButtonFinished_clicked();

36 signals:
37 void dataChangedSignal(bool);@

They are then used in addNew.cpp as follows:

@38 void addNew::on_pushButtonFinished_clicked()
39 {
40 if (addedData)
41 {
42 bool changed = true;
43 emit dataChangedSignal(changed);
44 }
45 this->close();
46 }@

I don't understand the problem of newDataSlot being declared void. It doesn't return any values, ad I thought that slots were required to be void.

I also don't understand "changed" not being declare in scope, since it is declared in pass.h on line 20.

It is quite possible that I don't fully understand the signals and slots concept or all the syntaxes involved, or is it some other dumb thing that
I have missed that has the compiler confused?

Can anyone help?