Add example of adapter pattern in C++

cpp/patterns/adapter/adapter.hpp

@@ -0,0 +1,37 @@
+
+#ifndef ADAPTER_HPP
+#define ADAPTER_HPP
+
+#include <random>
+
+// Target implementation to adapt to a new interface
+class Add {
+public:
+  virtual ~Add() = default;
+
+  virtual int doMath(const int &a, const int &b) const { return a + b;}
+};
+
+// An adaptee with some useful behavior to adapt to our Add target
+class RandomNumber {
+public:
+  explicit RandomNumber(const int &max) : maxNum(max) { srand(time(nullptr));}
+
+  int getRandom() const { return rand() % maxNum;}
+
+private:
+  int maxNum;
+};
+
+// An adapter that combines behaviors of Add and RandomNumber
+class RandomAddAdapter : public Add {
+public:
+  explicit RandomAddAdapter(RandomNumber *random_) : random(random_) {}
+
+  int doMath(const int &a, const int &b) const override { return a + b + random->getRandom();}
+
+private:
+  RandomNumber *random;
+};
+
+#endif // ADAPTER_HPP