add Facade pattern

facade/Facade.cpp

@@ -0,0 +1,83 @@
+/*
+ * C++ Design Patterns: Facade
+ * Author: Jakub Vojvoda [github.com/JakubVojvoda]
+ * 2016
+ *
+ * Source code is licensed under MIT licence
+ * (for more details see LICENCE)
+ *
+ */
+
+#include <iostream>
+
+/*
+ * Subsystems
+ * implement more complex subsystem functionality
+ * and have no knowledge of the facade
+ */
+class SubsystemA {
+public:
+  void suboperation() {
+    std::cout << "Subsystem A method" << std::endl;
+    // ...
+  }
+  // ...
+};
+
+class SubsystemB {
+public:
+  void suboperation() {
+    std::cout << "Subsystem B method" << std::endl;
+    // ...
+  }
+  // ...
+};
+
+class SubsystemC {
+public:
+  void suboperation() {
+    std::cout << "Subsystem C method" << std::endl;
+    // ...
+  }
+  // ...
+};
+
+/*
+ * Facade
+ * delegates client requests to appropriate subsystem object
+ * and unified interface that is easier to use
+ */
+class Facade {
+public:
+  Facade() :
+    subsystemA(), subsystemB(), subsystemC() {}
+
+  void operation1() {
+    subsystemA->suboperation();
+    subsystemB->suboperation();
+    // ...
+  }
+
+  void operation2() {
+    subsystemC->suboperation();
+    // ...
+  }
+
+  // ...
+
+private:
+  SubsystemA *subsystemA;
+  SubsystemB *subsystemB;
+  SubsystemC *subsystemC;
+  // ...
+};
+
+
+int main()
+{
+  Facade *facade = new Facade();
+  facade->operation1();
+  facade->operation2();
+
+  return 0;
+}

facade/README.md

@@ -2,6 +2,7 @@
 
 Provide a unified interface to a set of interfaces in a subsystem. Facade
 defines a higher-level interface that makes the subsystem easier to use. 
+The pattern has structural purpose and applies to objects.
 
 ### When to use