I am falling in love with events.
Events are implemented via delegates and are used for objects that communicate with multiple clients when a particular action occurs.
Scenario: there's a soccer game between England and Mexico. Both countries need to be informed when a goal was scored.
Step 1: create a class for goal event data.
public class GoalEventArgs : EventArgs
{
public readonly string Country;
public readonly string Player;
public readonly int minute;
public GoalEventArgs(string country, string player, int minute)
{
this.Country = country;
this.Player = player;
this.minute = minute;
}
}
Step 2: create a delegate for the event handler.
public delegate void AddGoalEventHandler(object sender, GoalEventArgs e);
Step 3: create the game class that will handle the event (make it static since only one game can be played at a time).
class Game
{
public event AddGoalEventHandler GoalEventHandler;
private static Game _instance = null;
static Game()
{
_instance = new Game();
}
private Game() { }
public static Game Singleton
{
get
{
return _instance;
}
}
public void GoalScored(string country, string player, int minute)
{
AddGoalEventHandler g = GoalEventHandler;
if (g != null)
g(null, new GoalEventArgs(country, player, minute));
}
}
Step 4: create a class for the Mexicans.
class Mexico
{
private static Game game;
public Mexico(Game g)
{
game = g;
game.GoalEventHandler += new AddGoalEventHandler(game_GoalEventHandler);
}
void game_GoalEventHandler(object sender, GoalEventArgs e)
{
if (e.Country.ToUpper().Equals("ENGLAND"))
Console.WriteLine("Ohh NO!!! ENGLAND JUST SCORED!!! That bastardo " + e.Player + " scored on minute " + e.minute.ToString());
else
Console.WriteLine("GOOOOAAAAALLLL!! VIVA MEXICO!!! " + e.Player + " has done it once again on minute " + e.minute.ToString());
}
}
Step 5: create a class for the English.
class England
{
private static Game game;
public England(Game g)
{
game = g;
game.GoalEventHandler += new AddGoalEventHandler(game_GoalEventHandler);
}
void game_GoalEventHandler(object sender, GoalEventArgs e)
{
if (e.Country.ToUpper().Equals("ENGLAND"))
Console.WriteLine("ENGLAND JUST SCORED!!! That hero" + e.Player + " scored on minute " + e.minute.ToString());
else
Console.WriteLine("NOOOOO!!! " + e.Player + " has done the unthinkable and scored on minute " + e.minute.ToString());
}
}
To test, add the following to your main method:
Game g = Game.Singleton;
Mexico mexico = new Mexico(g);
England england = new England(g);
g.GoalScored("england", "owen", 15);
g.GoalScored("mexico", "hernandez", 25);
Your console output will be the following after line 4 gets executed:
Your console output will be the following after line 5 gets executed:
As you can see, the possibilities with events are limitless!
