const QObject* overload for QMetaObject::invokeMethod

[Loic B.]

Hello,

I want to call QMetaObject::invokeMethod on a const QObject* but I see no overload accepting it as const. Why is there no overload ?

Is it safe to const_cast<QObject *> to call QMetaObject::invokeMethod ? Is this will invoke UB ?

[SGaist]

Hi,

How come you get a const QObject pointer to call invokeMethod with ?

[Loic B.]

@SGaist i want to ensure that some member function are called in the thread of the object to avoid data races mostly. I decided to implement a function accepting a function object containing thé code to execute. If the current thread is the object one, il directly invoke the function object with std::invoke. If not, i call the function object on the object context via QMetaObject::invokeMethod.

Some of the function i want to be called on the same thread are getters that I put const by default.

[Christian Ehrlicher]

@Loic-B said in const QObject* overload for QMetaObject::invokeMethod:

Some of the function i want to be called on the same thread are getters that I put const by default.

Then it's not a slot and there is no need that it's called via QMetaMethod.

[Loic B.]

@Christian-Ehrlicher so how can i ensure that without using the QMetaObject::invokeMethod ? By using mutexes ?

[Christian Ehrlicher]

@Loic-B said in const QObject* overload for QMetaObject::invokeMethod:

By using mutexes ?

If you access an object from different threads then you have to apply correct locking. Nothing Qt specific but Qt has a nice page about thread synchronization.