Question

Possible Duplicate:
When do I use a dot, arrow, or double colon to refer to members of a class in C++?

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

In the code above, what does -> mean? Thanks.

Answer 1

It means the object on the left side of the arrow is a pointer to an instance of a class or structure, and the name on the right is a member of that class or structure.

In the context:

ui->setupUI(this);

it means that ui is a pointer to an instance of the class Ui::MainWindow and the setupUI(this) is an invocation of the setupUI member function of that class with the parameter this.

When you have an actual instance of a class (or structure) instead of a pointer, then you use the notation:

Ui::MainWindow non_ptr; // not a pointer
non_ptr.setupUI(this);

Strictly, you can also write:

(*ui).setupUI(this);

However, you will rightly be ostracized if you write code like that rather than using the -> arrow operator.