About the Bridge pattern again

Question

I'm trying to understand the Bridge pattern. With examples from Wiki all is ok. But what if we have the next design:

How can I implement different remote controls (e.g. Infra-red and Wi-Fi)? Should I use Bridge pattern and how to do it? By analogy with an examples I need to combine all methods to the single wide interface with hardware implementation like on the next figure. But I don't think it's a good idea.

Answer 1

The bridge pattern is a lot like the adapter pattern.

Following your model, let's suppose you have an RemoteControl abstract class:

public abstract class RemoteControl
{
      protected HadwareRemoteControl hardwareBridge;

      //Can be injected using DI
      public RemoteControl(HadwareRemoteControl hardwareBridge)
      {
           this.hardwareBridge= hardwareBridge;
      }

      public void on()
      {
           hardwareBridge.on();
      }

      public void off()
      {
           hardwareBridge.off();
      }
}

And two implementations for that class:

public class TVRemoteControl extends RemoteControl
{
      public TVRemoteControl(TVHardwareRemoteControl hardwareBridge) {
           super(hardwareBridge);
      }

      public void nextChannel() {
           ((TVHardwareRemoteControl)hardwareBridge).nextChannel();
      }

      public void previousChannel() {
           ((TVHardwareRemoteControl)hardwareBridge).previousChannel();
      }
}

public class ModelRemoteControl extends RemoteControl
{
      public ModelRemoteControl (ModelHardwareRemoteControl hardwareBridge) {
           super(hardwareBridge);
      }

      public void moveForward() {
           ((ModelHardwareRemoteControl)hardwareBridge).moveForward();
      }

      public void moveBack() {
           ((ModelHardwareRemoteControl)hardwareBridge).moveBack();
      }     
}

Now, for the hardware bridge, we have a base interface:

public interface HadwareRemoteControl
{
      public void on();
      public void off();
}

And two more interfaces:

public interface TVHadwareRemoteControl extends HardwareRemoteControl
{
      public void nextChannel();
      public void previousChannel();
}

public interface ModelHardwareRemoteControl extends HardwareRemoteControl
{
      public void moveForward();
      public void moveBack();
}

And, as in your desing, two implementations:

public class InfraredRemoteControl implements TVHardwareRemoteControl, ModelHardwareRemoteControl
{
      public void on()
      {
         //Hardware Turn on
      }

      public void off()
      {
         //Hardware Turn off
      }

      public void nextChannel()
      {
         //Hardware Next channel
      }

      public void previousChannel()
      {
         //Hardware Previous channel
      }

      public void moveForward()
      {
         //Hardware Move Forward
      }

      public void moveBack()
      {
         //Hardware Move Back
      }
}


public class WifiRemoteControl implements TVHardwareRemoteControl, ModelHardwareRemoteControl
{
      public void on()
      {
         //Hardware Turn on
      }

      public void off()
      {
         //Hardware Turn off
      }

      public void nextChannel()
      {
         //Hardware Next channel
      }

      public void previousChannel()
      {
         //Hardware Previous channel
      }

      public void moveForward()
      {
         //Hardware Move Forward
      }

      public void moveBack()
      {
         //Hardware Move Back
      }
}

From an external project, a client of your API may use the hardware more transparently, not even aware of these implementations:

TVRemoteControl tvRemote = Factory.CreateTVRemote();

//Depending on the injected hardware implementation, it may call InfraredRemoteControl or WifiRemoteControl
tvRemote.on();
tvRemote.nextChannel();