operator + method
Adds a handler (callback) that will be executed when this Event is raised using the broadcast method.
Uses "+" as an alternative syntax to the subscribe method for adding a handler (callback) that will be executed when this Event is fired using the broadcast method.
// Example
counter.onValueChanged + (args) => print('value changed');
Implementation
void operator +(EventHandler<T> handler) {
subscribe(handler);
}