Xtykutl

I want to learn how/when/why to use the GoF Design Patterns. These last days are dedicated to the Bridge Pattern, which means:

Decouple an abstraction from its implementation so that the two can vary independently.

Everyone has a different understanding of this vague description, but if I well-understood the global point, it cuts an abstraction into multiple independant implementations which relies on each other, in a chain.

On this premise, let's try to implement a four-arrow remote control. First, let's define what's awaited with interfaces:

public interface ITopBottomButtonsControl

{

    void TopButtonPressed();

    void BottomButtonPressed();

}



public interface ILeftRightButtonsControl

{

    void LeftButtonPressed();

    void RightButtonPressed();

}



public interface IRemoteControl : 

    ILeftRightButtonsControl, 

    ITopBottomButtonsControl

{ }

Here is an example of the BP implementation:

public class ChannelControl : ILeftRightButtonsControl

{

    public void LeftButtonPressed() => Console.WriteLine("Previous channel");

    public void RightButtonPressed() => Console.WriteLine("Next channel");

}



public class ChapterControl : ILeftRightButtonsControl

{

    public void LeftButtonPressed() => Console.WriteLine("Previous chapter");

    public void RightButtonPressed() => Console.WriteLine("Next chapter");

}

public abstract class BPRemoteControl : IRemoteControl

{

    ILeftRightButtonsControl LeftRightControl { get; }



    public BPRemoteControl(ILeftRightButtonsControl leftRight)

    {

        LeftRightControl = leftRight;

    }



    public void LeftButtonPressed() => LeftRightControl.LeftButtonPressed();

    public void RightButtonPressed() => LeftRightControl.RightButtonPressed();



    public abstract void TopButtonPressed();

    public abstract void BottomButtonPressed();

}

public class SpeedControl : BPRemoteControl

{

    public SpeedControl(ILeftRightButtonsControl leftRight) : base(leftRight) { }



    public override void BottomButtonPressed() => Console.WriteLine("Slow down");

    public override void TopButtonPressed() => Console.WriteLine("Speed up");

}



public class VolumeControl : BPRemoteControl

{

    public VolumeControl(ILeftRightButtonsControl leftRight) : base(leftRight) { }



    public override void BottomButtonPressed() => Console.WriteLine("Volume down");

    public override void TopButtonPressed() => Console.WriteLine("Volume up");

}

The fact is that, when I implemented this to test the pattern, it made me think back the Entity Component System. So, I tried to implement the same application, but this time with an ECS approach.

The classes ChannelControl and ChapterControl remains the same, but the rest is different:

public class SpeedControl : ITopBottomButtonsControl

{

    public void BottomButtonPressed() => Console.Write("Slow down");

    public void TopButtonPressed() => Console.WriteLine("Speed up");

}



public class VolumeControl : ITopBottomButtonsControl

{

    public void BottomButtonPressed() => Console.WriteLine("Volume down");

    public void TopButtonPressed() => Console.WriteLine("Volume up");

}

public class ECSRemoteController : IRemoteControl

{

    private ITopBottomButtonsControl TopBottomButtonsComponent { get; }

    private ILeftRightButtonsControl LeftRightButtonsComponent { get; }



    public ECSRemoteController(ITopBottomButtonsControl topBottom, ILeftRightButtonsControl leftRight)

    {

        TopBottomButtonsComponent = topBottom;

        LeftRightButtonsComponent = leftRight;

    }



    public void TopButtonPressed() => TopBottomButtonsComponent.TopButtonPressed();

    public void BottomButtonPressed() => TopBottomButtonsComponent.BottomButtonPressed();



    public void LeftButtonPressed() => LeftRightButtonsComponent.LeftButtonPressed();

    public void RightButtonPressed() => LeftRightButtonsComponent.RightButtonPressed();

}

Finally, these two solutions seems to be the same, with the following difference:

The Bridge Pattern is vertically-organized: S(a -> b -> c)

The Entity-Component-System is horizontally-organized: S(a, b, c)

Is there really a difference between these two solutions? When should one be prefered to the other?

HOW TO TEST: separate the two solutions into two folders BridgePattern and EntityComponentPattern, and fill the console application with the following code:

    static void Main(string args)

    {

        BridgePattern();

        Console.WriteLine();

        EntityComponentSystem();

        Console.ReadLine();

    }



    static void BridgePattern()

    {

        Console.ForegroundColor = ConsoleColor.Cyan;

        Console.WriteLine("BridgePattern version");

        Console.WriteLine("----------");



        IRemoteControl TVRemoteControl = new BridgePattern.VolumeControl(new BridgePattern.ChannelControl());

        IRemoteControl DVDRemoteControl = new BridgePattern.SpeedControl(new BridgePattern.ChapterControl());



        Console.WriteLine($"1. {nameof(TVRemoteControl)}:");

        UseRemoteControl(TVRemoteControl);



        Console.WriteLine($"2. {nameof(DVDRemoteControl)}:");

        UseRemoteControl(DVDRemoteControl);

    }



    static void EntityComponentSystem()

    {

        Console.ForegroundColor = ConsoleColor.Yellow;

        Console.WriteLine("EntityComponentSystem version");

        Console.WriteLine("----------");



        IRemoteControl TVRemoteControl = new EntityComponentSystem.ECSRemoteController(new EntityComponentSystem.VolumeControl(), new EntityComponentSystem.ChannelControl());

        IRemoteControl DVDRemoteControl = new EntityComponentSystem.ECSRemoteController(new EntityComponentSystem.SpeedControl(), new EntityComponentSystem.ChapterControl());



        Console.WriteLine($"1. {nameof(TVRemoteControl)}:");

        UseRemoteControl(TVRemoteControl);



        Console.WriteLine($"2. {nameof(DVDRemoteControl)}:");

        UseRemoteControl(DVDRemoteControl);

    }



    static void UseRemoteControl(IRemoteControl remoteControl)

    {

        remoteControl.LeftButtonPressed();

        remoteControl.RightButtonPressed();

        remoteControl.TopButtonPressed();

        remoteControl.BottomButtonPressed();

    }