Added command example source code.

examples/behavioral/command.cpp

@@ -0,0 +1,108 @@
+#include <iostream>
+#include <memory>
+
+// The receiver.
+class Bulb
+{
+  public:
+    void turnOn(void)
+    {
+      std::cout << "Bulb has been lit." << std::endl;
+    }
+
+    void turnOff(void)
+    {
+      std::cout << "Darkness!" << std::endl;
+    }
+};
+
+class Command
+{
+  public:
+    virtual void execute(void) = 0;
+    virtual void undo(void) = 0;
+    virtual void redo(void) = 0;
+};
+
+// A command.
+class TurnOn : public Command
+{
+  public:
+    TurnOn(std::shared_ptr<Bulb> bulb)
+        : bulb_(bulb)
+    {
+    }
+
+    void execute(void)
+    {
+      bulb_->turnOn();
+    }
+
+    void undo(void)
+    {
+      bulb_->turnOff();
+    }
+
+    void redo(void)
+    {
+      execute();
+    }
+
+  private:
+    std::shared_ptr<Bulb> bulb_;
+};
+
+// Another command.
+class TurnOff : public Command
+{
+  public:
+    TurnOff(std::shared_ptr<Bulb> bulb)
+        : bulb_(bulb)
+    {
+    }
+
+    void execute(void)
+    {
+      bulb_->turnOff();
+    }
+
+    void undo(void)
+    {
+      bulb_->turnOn();
+    }
+
+    void redo(void)
+    {
+      execute();
+    }
+
+  private:
+    std::shared_ptr<Bulb> bulb_;
+};
+
+// The invoker.
+class RemoteControl
+{
+  public:
+    void submit(std::shared_ptr<Command> command)
+    {
+      command->execute();
+    }
+};
+
+int main()
+{
+  std::shared_ptr<Bulb> bulb = std::make_shared<Bulb>();
+
+  std::shared_ptr<TurnOn> turnOn = std::make_shared<TurnOn>(bulb);
+  std::shared_ptr<TurnOff> turnOff = std::make_shared<TurnOff>(bulb);
+
+  RemoteControl remote;
+  remote.submit(turnOn);
+  remote.submit(turnOff);
+  // Output:
+  // Bulb has been lit.
+  // Darkness!
+
+  return 0;
+}