using QTConcurrent with qhash

abdullahzubair109

beginner question : i have a QHash.. i am trying to call value method on it under QtConcurrent

QFuture<const int> future = QtConcurrent::run(editorList, &QHash<QString, int>::value, key);

compiler shows following error :

/usr/include/x86_64-linux-gnu/qt5/QtConcurrent/qtconcurrentrunbase.h:90:7: error: uninitialized const member in ‘const int’ [-fpermissive]
 class RunFunctionTask : public RunFunctionTaskBase<T>

i know i have to initialize const members.. but how??

SGaist

Hi,

What exactly are you trying to accomplish with that QtConcurrent::run ?

abdullahzubair109

@SGaist i want to find out value from QHash using key..this function :
https://doc.qt.io/qt-5/qhash.html#value

abdullahzubair109

@abdullahzubair109 as the QHash is really large, so i was trying to run it in concurrent to prevent gui freezing

SGaist

May I suggest an alternative ?

QFuture<int> future = QtConcurrent::run([=](){ return editorList.value(key); });

On a side note, calling a hash editorList is pretty confusing.

abdullahzubair109

@SGaist AFAIK lmbda are from c++ 11 .. I am using old c++ 98 .. One more thing : editorList records some QPlainTextEdit*

abdullahzubair109

@SGaist well I am convinced to name it something more representative

SGaist

What version of Qt 5 are you using ?

This QtConcurrent::run(editorList, &QHash<QString, int>::value, key); basically mean that you want to run the QHash::value method on your editorList variable. There's some kind of issue with the logic here.

abdullahzubair109

@SGaist qt 5.5

abdullahzubair109

@SGaist i had to use lambda finally.. so marking it solved.