QMap contains() + value() - better way?

[Vadi2]

I've got the following bit of code:

if (dockWindowConsoleMap.contains(windowName)) {
  font = dockWindowConsoleMap.value(windowName)->mUpperPane->mDisplayFont;

It's tidy, it's safe, but my static analyser complains about the impossible case that I'm doing a null pointer dereference with value() because of the default-constructed argument. It's an impossible case because of the contains() check but it's not smart enough.

I don't want to mark every time I use this pattern as a false positive in the static analyser - what's a better way to get a value from a QMap that's static-analysis friendly?

[kshegunov]

You can try with QMap::find() and then QMap::Iterator::value() if the returned iterator isn't equal to QMap::end():

QMap< ... >::Iterator element = dockWindowConsoleMap.find(windowName);
if (element != dockWindowConsoleMap.end())
     font = element.value()->mUpperPane->mDisplayFont;

[VRonin]

While @kshegunov suggests a correct efficency improvement, I doubt it will solve your problem as it's triggered by mUpperPane-> not what's on the left. Q_ASSERT should solve it though.

const auto element = dockWindowConsoleMap.constFind(windowName);
if (element != dockWindowConsoleMap.cend()){
Q_ASSERT(element.value()->mUpperPane);
font = element.value()->mUpperPane->mDisplayFont;
}

[Vadi2]

I see. Thank you both for the responses.