- Qt 5.15
- Qt Core
- C++ Classes
- QException
- Qt 5.15.18 Reference Documentation

# QException Class

The QException class provides a base class for exceptions that can transferred across threads. More...

Header: | #include <QException>
qmake: | QT += core
Since: | Qt 5.0
Inherited By: | QUnhandledException

This class was introduced in Qt 5.0.

- List of all members, including inherited members

## Public Functions

virtual QException * | clone() const
virtual void | raise() const

## Detailed Description

Qt Concurrent supports throwing and catching exceptions across thread boundaries, provided that the exception inherit from QException and implement two helper functions:

     class MyException : public QException
     {
     public:
         void raise() const override { throw *this; }
         MyException *clone() const override { return new MyException(*this); }
     };

QException subclasses must be thrown by value and caught by reference:

     try  {
         QtConcurrent::blockingMap(list, throwFunction); // throwFunction throws MyException
     } catch (MyException &e) {
         // handle exception
     }

If you throw an exception that is not a subclass of QException, the Qt functions will throw a QUnhandledException in the receiver thread.

When using QFuture, transferred exceptions will be thrown when calling the following functions:

- QFuture::waitForFinished()
- QFuture::result()
- QFuture::resultAt()
- QFuture::results()

## Member Function Documentation

### `[virtual]` QException *QException::clone() const

In your QException subclass, reimplement clone() like this:

     MyException *MyException::clone() const { return new MyException(*this); }

### `[virtual]` void QException::raise() const

In your QException subclass, reimplement raise() like this:

     void MyException::raise() const { throw *this; }