Add command pattern

Author: joaofnds

command-pattern.ts

@@ -0,0 +1,137 @@
+/**
+ * What is the Command Design Pattern?
+ *
+ * - The command pattern is a behavioural design pattern in which an object is
+ *   used to represent and encapsulate all the information needed to call
+ *   a method at a later time
+ * - This information includes the method name, the object that owns the method
+ *   and values for the method parameters
+ * - Allows you to store lists of code that is used at a later time
+ *   or many times
+ * - Client says "I want a specific Command to run when execute() is called on
+ *   one of these encapsulated(hidden) Objects"
+ * - An Object called the Invoker transfers this Command to another Object
+ *   called a Receiver to execute the right code
+ *
+ * @see http://www.newthinktank.com/2012/09/command-design-pattern-tutorial/
+ */
+
+interface ElectronicDevice {
+  on(): void;
+  off(): void;
+  volumeUp(): void;
+  volumeDown(): void;
+}
+
+class Television implements ElectronicDevice {
+  private volume: number = 0;
+  on(): void {
+    console.log("TV is ON")
+  }
+  off(): void {
+    console.log("TV is OFF")
+  }
+  volumeUp(): void {
+    this.volume++;
+    this.displayVolume();
+  }
+  volumeDown(): void {
+    this.volume--;
+    this.displayVolume();
+  }
+  private displayVolume() {
+    console.log(`TV Volume is at ${this.volume}`)
+  }
+}
+
+interface Command {
+  execute(): void;
+}
+
+class TurnTVOn implements Command {
+  private device: ElectronicDevice;
+
+  public constructor(device: ElectronicDevice) {
+    this.device = device;
+  }
+
+  execute(): void {
+    this.device.on();
+  }
+}
+
+class TurnTVOff implements Command {
+  private device: ElectronicDevice;
+
+  public constructor(device: ElectronicDevice) {
+    this.device = device;
+  }
+
+  execute(): void {
+    this.device.off();
+  }
+}
+
+class TurnTVUp implements Command {
+  private device: ElectronicDevice;
+
+  public constructor(device: ElectronicDevice) {
+    this.device = device;
+  }
+
+  execute(): void {
+    this.device.volumeUp();
+  }
+}
+
+class TurnTVDown implements Command {
+  private device: ElectronicDevice;
+
+  public constructor(device: ElectronicDevice) {
+    this.device = device;
+  }
+
+  execute(): void {
+    this.device.volumeDown();
+  }
+}
+
+class DeviceButton {
+  private command: Command;
+
+  public constructor(command: Command) {
+    this.command = command;
+  }
+
+  public press(): void {
+    this.command.execute();
+  }
+}
+
+class TVRemote {
+  public static getDevice(): ElectronicDevice {
+    return new Television();
+  }
+}
+
+//------------------------------------------------------------------------------
+
+const device: ElectronicDevice = TVRemote.getDevice();
+
+const commands: { [key: string]: Command } = {
+  on: new TurnTVOn(device),
+  off: new TurnTVOff(device),
+  up: new TurnTVUp(device),
+  down: new TurnTVDown(device)
+}
+const buttons: { [key: string]: DeviceButton } = {
+  on: new DeviceButton(commands.on),
+  off: new DeviceButton(commands.off),
+  up: new DeviceButton(commands.up),
+  down: new DeviceButton(commands.down),
+}
+
+buttons.off.press();
+buttons.on.press();
+buttons.up.press();
+buttons.down.press();