Slot typedef

Slot = void

Signals help you to establish connections between two entities.

It is essentially a communication mechanism. When an entity wants to notify others about something, it creates an signal and emit it. It doesn't care about who wants to listen to the signal. The interested parties will connect to the signal instead. They will disconnect from the signal when there's no more need to listen to it.

Let us create a class that will emit signals for others to connect to.

 class SignalEmitter {
    final somethingHappened = Signal();
 }

Let's create another class that is interested in listening to the signal we just created.

class SignalReceiver {
  Slot handleSomethingHappened() {
    print("something happened.");
  }

!Note: Slot is just a typedef for void. It is used to highlight that the method is intended to be used as a slot.

Connect the slot to the signal to get notified about signal emission.

  signalEmitter.somethingHappened.connect(signalReceiver.handleSomethingHappened);
  //connect(signalEmitter.somethingHappened, signalReceiver.handleSomethingHappened); <- or like this

Now we will emit the signal to notify others.

signalEmitter.somethingHappened();

Running the code would print "something happened."

Disconnect the slot from the signal when it is no more needed.

  signalEmitter.somethingHappened.disconnect(signalReceiver.handleSomethingHappened);
  //disconnect(signalEmitter.somethingHappened, signalReceiver.handleSomethingHappened); <- or like this

Helps visually distinguishing between slots and other methods. Not necessary to use but helpful for void slots. Slots must be a function with at most one argument.

Implementation

/// Helps visually distinguishing between slots and other methods.
/// Not necessary to use but helpful for void slots.
/// Slots must be a function with at most one argument.
typedef Slot = void;