Added proxy example source code.

examples/structural/proxy.cpp

@@ -0,0 +1,68 @@
+#include <iostream>
+#include <memory>
+#include <string>
+
+class Door
+{
+  public:
+    typedef std::shared_ptr<Door> ptr_t;
+    virtual void open(void) = 0;
+    virtual void close(void) = 0;
+};
+
+class LabDoor : public Door
+{
+  public:
+    void open(void)
+    {
+      std::cout << "Opening lab door" << std::endl;
+    }
+
+    void close(void)
+    {
+      std::cout << "Closing lab door" << std::endl;
+    }
+};
+
+class SecuredDoor
+{
+  public:
+    SecuredDoor(Door::ptr_t door)
+        : door_(door)
+    {
+    }
+
+    void open(const std::string& password)
+    {
+      if (authenticate(password)) {
+        door_->open();
+      } else {
+        std::cout << "No way, Jose!" << std::endl;
+      }
+    }
+
+    void close(void)
+    {
+      door_->close();
+    }
+
+  private:
+    bool authenticate(const std::string& password)
+    {
+      return password == "Bond007";
+    }
+
+    Door::ptr_t door_;
+};
+
+int main()
+{
+  Door::ptr_t labDoor = std::make_shared<LabDoor>();
+  SecuredDoor securedDoor(labDoor);
+
+  securedDoor.open("invalid"); // Output: No way, Jose!
+  securedDoor.open("Bond007"); // Output: Opening lab door
+  securedDoor.close(); // Output: Closing lab door
+
+  return 0;
+}