Error: reference to type 'NBhistoryItem *const' could not bind to an lvalue of type 'const NBhistoryItem *'

nicky j

Hello,

I am getting this error:
error: reference to type 'NBhistoryItem *const' could not bind to an lvalue of type 'const NBhistoryItem *'

whenever the following code is called:
void NBhistoryInterface::addHistoryItem(const NBhistoryItem *input)
@
{
qDebug() << "SLOT: NBhistoryInterface::addHistoryItem(const NBhistoryItem &input) STATUS: Called";
m_history.prepend(input);
qDebug() << "SLOT: NBhistoryInterface::addHistoryItem(const NBhistoryItem &input) STATUS: Completed";
}
@

m_history is a QList<NBhistoryItem*>

What am I doing wrong?

Thanks!

ChrisW67

Your list is of pointers to non-const NBhistoryItems and you are trying to prepend a pointer to a const NBhistoryItem.

nicky j

okay, so then what should it look like?

ChrisW67

Either this (if the NBhistoryItems should be modifiable through the pointers in the list):
@
QList<NBhistoryItem*> m_list;

void NBhistoryInterface::addHistoryItem(NBhistoryItem input)
{
m_history.prepend(input);
}
@
or this (if the list should be pointing to const NBhistoryItems):
@
QList<const NBhistoryItem> m_list;

void NBhistoryInterface::addHistoryItem(const NBhistoryItem *input)
{
m_history.prepend(input);
}
@

nicky j

Ok changed it to the first option you gave:

@
void NBhistoryInterface::addHistoryItem(NBhistoryItem *input)
{
qDebug() << "SLOT: NBhistoryInterface::addHistoryItem(const NBhistoryItem &input) STATUS: Called";
m_history.prepend(input);
qDebug() << "SLOT: NBhistoryInterface::addHistoryItem(const NBhistoryItem &input) STATUS: Completed";
}
@

The program compiles then crashes. Heres what the crash report gives me:

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 @BUNDLEIDENTIFIER@ 0x0000000100018364 QList<NBhistoryItem*>::prepend(NBhistoryItem* const&) + 20 (qlist.h:546)
1 @BUNDLEIDENTIFIER@ 0x000000010001795e NBhistoryInterface::addHistoryItem(NBhistoryItem*) + 142 (nbhistory.cpp:

ChrisW67

Did you recompile the everything in the code that uses that NBhistoryInterface::addHistoryItem() interface?

nicky j

yes, I believe everything has been recompiled. Maybe the problem has to do with the slot calling addHistoryItem(), but I don't think so. Here it is anyway though:
@
void NBhistoryInterface::addHistoryEntry(const QUrl &url)
{
QUrl historyUrl = url;
NBhistoryItem *item = new NBhistoryItem("url", "title");
addHistoryItem(item);
}

void NBhistoryInterface::addHistoryItem(NBhistoryItem *input)
{
qDebug() << "SLOT: NBhistoryInterface::addHistoryItem(const NBhistoryItem &input) STATUS: Called";
m_history.prepend(input);
qDebug() << "SLOT: NBhistoryInterface::addHistoryItem(const NBhistoryItem &input) STATUS: Completed";
}

QList<NBhistoryItem*> m_history;
@

Thanks for the help!