Question

I’m writing a simple game in XNA and I’ve faced a problem with delegates. I use them to represent physics in the game, e.g.:

public delegate void PhysicsLaw(World world);

//for gravitation
static public void BallLawForGravity(World world)
        {
            if (world.ball.position.Y != world.zeroLevel)
                //v(t) = v0 + sqrt(c * (h - zeroLevel))
                world.ball.speed.Y += (float)Math.Sqrt(0.019 * (world.zeroLevel - world.ball.position.Y)); 
        }

And I want to create multicast delegates for different objects/circumstances consisting from many methods such as BallLawForGravity(), but I can do it only like this:

processingList = BallLawForBounce;
processingList += BallLawForAirFriction;
...
processingList += BallLawForGravity;

Obviously, it doesn’t look good. Is there any standard way to create a multicast delegate from collection of method names?

Answer 1

Use the static method Delegate.Combine Method (Delegate[]) for such tasks.

 PhysicsLaw[] delegates = new PhysicsLaw[] {
        new PhysicsLaw( PhysicsLaw ),
        new PhysicsLaw( BallLawForAirFriction )
    };

    PhysicsLaw chained = (PhysicsLaw) Delegate.Combine( delegates );
    chained(world);

More examples.

Update
You can use the creating delegate via Reflection for this but I don’t recommend it, because it’s very slow technic.