[Qt-interest] )

[Pete Christensen]

andrew.m.goth at l-3com.com wrote:
> Bob Hood wrote:
>> Scott Aron Bloom wrote:
>>> Simply making it a QFile *, and then in the constructor, creating a
>>> blank QFile...
>> Remembering, of course, to delete it in your destructor
> 
> QFile is derived from QObject, so you should use Qt's object ownership
> mechanism.  When you create the QFile, pass a parent (owning) object
> pointer to its constructor.  That parent object's QObject destructor
> will automatically delete the QFile for you.
> 
> Of course, this assumes there *is* a parent QObject to point to, which
> won't be the case if you are putting this QFile* in a class that is not
> derived from QObject or one of its subclasses.  In this situation, you
> will have to manually delete the QFile* when you're done with it.
> 
> Class definition:
> 
> MyClass: public QObject {
> Q_OBJECT
> public:
>     MyClass(QObject* parent = 0);
> protected:
>     QFile* file;
> };
> 
> Constructor (approach #1):
> 
> MyClass::MyClass(QObject* parent):
>     QObject(parent),
>     file(new QFile(this))
> {}
> 
> Constructor (approach #2):
> 
> MyClass::MyClass(QObject* parent):
>     QObject(parent)
> {
>     file = new QFile(this);
> }
> 
> You can also pass a filename to QFile's constructor.
> 

Excellent information, thanks Andy. It's the nudge I needed to use 
QObject inheritance properly. For confirmation, I dug around in the 
object model documentation and found this:

file:///usr/share/qt4/doc/html/qobject.html#no-copy-constructor

This basically says, "You should use pointers to QObject (or to your 
QObject subclass) where you might otherwise be tempted to use your 
QObject subclass as a value." I'm pretty sure this describes my 
situation, since QFile is a subclass of QObject. Wish I'd found that 
before I posted here :)

I ended up passing the QString for the QFile constructor through 
"MyClass" to a QThread and then I created and read a QTextStream in the 
QThread's run(). So far that approach seems to work fine. (For 
interest's sake, I could declare "private: QString fileName" in my 
QThread since QString doesn't inherit from QObject :D)

Thanks again,
Pete