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Command Pattern

Command Pattern. Encapsulation Invocation. One size fits all. Vender Classes. Intro to Command Pattern. Interaction in detail. Encapsulation. An order Slip encapsulates a request to prepare a meal. The waitress's job is to take order Slips and invoke the orderUp () method on them.

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Command Pattern

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  1. Command Pattern Encapsulation Invocation

  2. One size fits all

  3. Vender Classes

  4. Intro to Command Pattern

  5. Interaction in detail

  6. Encapsulation • An order Slip encapsulates a request to prepare a meal. • The waitress's job is to take order Slips and invoke the orderUp() method on them. • The Cook has the knowledge required to prepare the meal.

  7. API interface??

  8. From Dinner to Command Pattern

  9. Our first command object public interface Command { public void execute(); } Implementing Command to turn light on public class LightOnCommand implements Command { public LigthOnCommand(Light light) { this.light = light; } public void execute(){ light.on(); } } Light on() off()

  10. Using Command object public class SimpleRemoteControl { Command slot; public SimpleRemoteControl() { } public void setCommand(Command command) { slot = command; } public void buttonWasPresses() { slot.execute(); } }

  11. Creating a simple test public class RemoteControlTest { public static void main(String[] args) { SimpleRemoteControl remote = new SimpleRemoteControl(); Light light = new Light(); GarageDoorgarageDoor = new GarageDoor(); LightOnCommandlightOn = new LightOnCommand(light); GarageDoorOpenCommandgarageOpen = new GarageDoorOpenCommand(garageDoor); remote.setCommand(lightOn); remote.buttonWasPressed(); remote.setCommand(garageOpen); remote.buttonWasPressed(); } }

  12. Command Pattern Defined The Command Pattern encapsulates a request as an object; thereby letting you parameterize other objects with different requests, queue or log requests, and support undoable operations.

  13. public class RemoteControl { Command[] onCommands; Command[] offCommands; public RemoteControl() { onCommands = new Command[7]; offCommands = new Command[7]; Command noCommand = new NoCommand(); for (inti = 0; i < 7; i++) { onCommands[i] = noCommand; offCommands[i] = noCommand; } } public void setCommand(int slot, Command onCommand, Command offCommand) { onCommands[slot] = onCommand; offCommands[slot] = offCommand; } public void onButtonWasPushed(int slot) { onCommands[slot].execute(); } public void offButtonWasPushed(int slot) { offCommands[slot].execute(); } }}

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