public Car(TrainSignal trainSig, string name)
{
Name = name;
// !!observer pattern!!
trainSig.TrainsAComing += StopTheCar;
}
public static void TestUseDelegate()
{
TrainSignal trainSignal = new TrainSignal();
new Car(trainSignal);
new Car(trainSignal);
new Car(trainSignal);
new Car(trainSignal);
trainSignal.HereComesTheTain();
}
static void Main()
{
TrainSignal signal = new TrainSignal();
Train train = new Train();
LevelCrossing crossing = new LevelCrossing();
WarningSiren siren = new WarningSiren();
crossing.registerToSignal(signal);
train.registerSignal(signal);
siren.registerToSignal(signal);
signal.setSignal(signalColour.green);
siren.respondToSignal(signalColour.green);
signal.setSignal(signalColour.red);
siren.respondToSignal(signalColour.red);
signal.setSignal(signalColour.green);
siren.respondToSignal(signalColour.green);
}
// delegates allow references to methods with a matching signature, and can invoke that method through the delegate instanace.
// events are delegate references with two restrictions:
// you CANT invoke the delegate reference directly
// you CANT assign to the delegate reference directly
// under the hood, it privatizes the field
void Start()
{
TrainSignal trainSignal = new TrainSignal();
new Car(trainSignal, "Ferrari");
new Car(trainSignal, "Volvo");
new Car(trainSignal, "Bus");
trainSignal.HereComesATrain();
// being NAUGHTY, invoking the delegate directly
trainSignal.TrainsAComing();
//being VERY NAUGHTY, nulling out the delegate
trainSignal.TrainsAComing = null;
// now we loose reference to the delegate
trainSignal.HereComesATrain();
}
public Car(TrainSignal trainSignal)
{
trainSignal.TrainsAreComing += StopTheCar; // construct the list
}
public void registerToSignal(TrainSignal signal)
{
signal.onSignalChange += new lightChangeHandler(respondToSignal);
}