A slot is a type of computer processor connection. It is a special connection for one user on a server. In addition, it can be used for receiving signals.
A slot can be defined as virtual slot demo or physical. Using a virtual slot, you can have a slot that will invoke a function in another class. This is useful in case your slot needs to receive a signal from a different class.
Slots are a form of public access function in C++. They follow normal C++ rules when called directly. However, they are slightly slower than callbacks.
Slots are usually invoked by the component that emitted the signal. When called, they have to pass an overhead to safely iterate over all connections. Compared to the overhead that is required by any operation, this is very low.
The QObject::connect method can be used to connect a signal to a slot. The function uses a SLOT macro and a SIGNAL macro to call the slot. These macros are used by the compiler to check compatibility.
Slots are also useful for emitting signals. The mechanism is very simple. Emitting signals connected to slots is ten times slower than calling the receiver directly.
Slots are normally implemented as member functions. If the slots are virtual, they can be called by any component. For instance, a DOM tree can be connected to a slot.
Some slots are private, and can only be invoked in unrelated classes. That’s why signals connected to them should be emitted from a class that defines them.