Why using QMetaObject::invokeMethod when executing method from thread
c++, multithreading, qt, qthread
Solution
As you haven't specified a `Qt::ConnectionType`, the method will be invoked as `Qt::AutoConnection`, which means that it will be invoked synchronously (like a normal function call) if the object's thread affinity is to the current thread, and asynchronously otherwise. "Asynchronously" means that a `QEvent` is constructed and pushed onto the message queue, and will be processed when the event loop reaches it.
The reason to use `QMetaObject::invokeMethod` if the recipient object might be in another thread is that attempting to call a slot directly on an object in another thread can lead to corruption or worse if it accesses or modifies non-thread-safe data.
Problem
I have following code: ``` class A : public QObject { Q_OBJECT public: A() : QObject() { moveToThread(&t); t.start(); } ~A() { t.quit(); t.wait(); } void doSomething() { QMetaObject::invokeMethod(this,"doSomethingSlot"); } public slots: void doSomethingSlot() { //do something emit ready(); } signals: void ready(); private: QThread t; } ``` The question why from `doSomething` it must be call via `QMetaObject::invokeMethod`. I know that there is something with connection type. Could some one explain what is under the hood?