[SOLVED] can't return a qstring

[kalster]

when i return i value in the changePixmap function, the value returns it incorrectly. i am calling the function changePixmap from within the mainwindow constructor. yet when it returns, i get a blank message. it should return "test". what am i doing wrong?

@MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
changePixmap();
ui->textEdit->setText(message);
}

QString const MainWindow::changePixmap(message)
{
QString message="test";
return message;
}@

[JohanSolo]

Apparently you're overwriting the content of message, since it's the method argument AND a local variable. But the method declaration seems weird to me... at least a type is expected, you're only giving a variable.

[kalster]

i don't understand what you are saying. i am getting an error expected ',' or ';' before '{' token at the beginning of the function.

[JohanSolo]

Well, your method should look like

QString const MainWindow::changePixmap( type message )
{
  QString message="test";
  return message;
}

With the correct type you need (I can't guess...), but then the argument message will be shadowed by the QString message which is declared in the method's body.

[octal]

I guess what you're trying to do is :

@
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
const QString message = changePixmap();
ui->textEdit->setText(message);
}

QString MainWindow::changePixmap()
{
QString message = "test";
return message;
}
@

Here, you call the changePixmap member function and put the return into a local (const-qualified) message variable.

[kalster]

i changed it do the following...

@QString const MainWindow::changePixmap( QString message )@
now i get an error no matching function for call to 'MainWindow::changePixmap()'

in the head i have, QString changePixmap(QString message);

[JohanSolo]

If your method is just returning a QString, it doesn't need to have any argument at all! Octal's suggestion should just be fine!

[Robbin]

The method declaration should be absolutely the same in your header file and in your implementation file,
If you have
@
QString changePixmap(QString message);
@
in your header file, your implementation should be
@
QString MainWindow::changePixmap(QString message)
@
Match the types exactly.....

[Robbin]

uhm, and yeah, octal is right, you don't need the argument at all in this case

[kalster]

ya that worked octal. thank you

[Rahul Das]

Calling function and the fuction you are expecting to be called are different [in signature].
changePixmap() is NOT changePixmap(message)
You should define changePixmap() separately, if you are looking for polymorphism.

And Like Octal said, there is a missing type for the formal parameter.
EDIT : post was bit late, as the window was not refreshed :(
[quote author="kalster" date="1314771307"]when i return i value in the changePixmap function, the value returns it incorrectly. i am calling the function changePixmap from within the mainwindow constructor. yet when it returns, i get a blank message. it should return "test". what am i doing wrong?

@
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
changePixmap();
ui->textEdit->setText(message);
}

QString const MainWindow::changePixmap(message)
{
QString message="test";
return message;
}
@
[/quote]

[kalster]

thank you Rahul Das for your post. every bit of information helps me to understand qt a bit more. :)

yes octal solved this topic.

[giesbert]

Hi kalster, just as a ide node. Those are no Qt issues, those are basic C++ issues.

[kalster]

yes i know. i made a mistake when i posted the message about understanding qt a bit more. i should have said c++.