Feed a QList with another

Question

hi i'm trying to send a QList as a parameter to another class but for some reason i got a read access violation...

CompareTimeChannel.h

 class CompareTimeChannel : public IDataChannel
   public:

      // @brief The method used to receive the list
      void setData(const QList< QSharedPointer<core::ITrackSection> > & sections);

      // @brief The list
      QList< QSharedPointer<core::ITrackSection> > _sections;

 };

CompareTimeChannel.cpp

 // @brief Empty constructor
 CompareTimeChannel::CompareTimeChannel()
 {
 }

 void CompareTimeChannel::setData(const QList< QSharedPointer<core::ITrackSection> > & sections)
 {
     //_sections = *new QList< QSharedPointer<core::ITrackSection> > ();
     _sections.clear();
     _sections.append(sections);
 }

Running this code will throw Exception at 0x31cc78d, code: 0xc0000005: read access violation at: 0x4, flags=0x0 on _sections.clear();

I tried to initialize the list before (the commented line _sections = *new QList<...>) but the exception is thrown the same.

An answer would be very appreciated...

EDIT

Ok it's fixed!

First, like @AndreasT said, i had to initialize the default QList constructor.

Then, according to @10WaRRioR01 's answer, the issue comes from CompareTimeChannel which wasn't initialized the first time the method was called. Fixed using :

        CompareTimeChannel* chan = static_cast<CompareTimeChannel*>(channel);
        Q_ASSERT(chan);
        if (chan) {
            chan->setData(sections);
        }
        else {
            qDebug() << "Dynamic cast failure";
        }

Thank you all, guys!

Answer 1

//_sections = *new QList< QSharedPointer<core::ITrackSection> > ();

You shouldn't ever do something like this. This creates a new instance of QList on the heap and it will never be deleted, so you have a memory leak
You should have done

_sections = QList< QSharedPointer<core::ITrackSection> > ();

instead, and it would be legal. But the most simple way is to use a copy assignment like this

_sections = sections

The problem you got is most likely related to the data you have in _sections. Maybe you are calling your methods on a null CompareTimeChannel object