Additional parameters für QObject class?

syfy323

This is a very basic question.

I have a class named HddAllocation:

@class HddAllocation : public QObject
{
Q_OBJECT
public:
explicit HddAllocation(QObject *parent = 0, const wchar_t * mountPoint = L"C:\");@
...

Without >, const wchar_t * mountPoint = L"C:\"< I can create a new class easily. I just want to append a single parameter.

@HddAllocation::HddAllocation(QObject *parent, const wchar_t * mountPoint) :
QObject(parent)
{
lpDirectoryName = mountPoint;
lpFreeBytesAvailable = new ULARGE_INTEGER;
lpTotalNumberOfBytes = new ULARGE_INTEGER;
lpTotalNumberOfFreeBytes = new ULARGE_INTEGER;

}@

Doing this forces me to provide a QObject parent. But how?

Thanks.

koahnig

You can change the sequence of the parameters, if you do not want to provide an instance for the QObject.

@
class HddAllocation : public QObject
{
Q_OBJECT
public:
explicit HddAllocation(const wchar_t * mountPoint, QObject *parent = 0 );
@

I have removed the default parameter. So you have to provide a parameter. I would assume that the compiler complained with your initialization of the default for mountPoint anyhow. At least I did not understand what the extra 'L' was for.

@
HddAllocation::HddAllocation(const wchar_t * mountPoint, QObject *parent ) :
QObject(parent)
{
lpDirectoryName = mountPoint;
lpFreeBytesAvailable = new ULARGE_INTEGER;
lpTotalNumberOfBytes = new ULARGE_INTEGER;
lpTotalNumberOfFreeBytes = new ULARGE_INTEGER;
}
@

syfy323

Thanks! This is exactly what I needed.

The "L" in front of the string is for wide string literals, represented as L"xxx".
http://msdn.microsoft.com/en-us/library/69ze775t.aspx

I am currently integrating some Win32 API functions in my app.

Thanks for your help, my class is now working! ;-)

koahnig

Thanks that is explaining it. I typically stay with standard ASCII chars.
Here is also a "link from a more neutral source":http://en.cppreference.com/w/cpp/language/string_literal

Since you are apparently learning C++ you might want to check also such information sources. MSDN has great detailed information which is really useful. However, out of personal experience I would recommend to do those checks. Otherwise you may face have trouble to migrate to other platforms without ms compiler.