Odd compiler error on a signal & slot
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I am trying to pass some data to the main window from a child window before closing the child window, and get the following compiler errors:
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?
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Slots do not have to be void
You lack Q_OBJECT macro in pass.h
line 27: you have not specified the variable type (should be bool changed)
the slot is declared private which may cause problems
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Thanks for the help.
The problem was in the private declaration of the slot. I didn't have to think about it very hard after you pointed it out why it made no sense to declare it as private.
BTW, I did have Q_OBJECT included, I just didn't show it in the snippets.
thx again!
