Jiwan · February 3, 2016 21:19 · Feb 3, 2016
diff --git a/repository_base.cpp b/repository_base.cpp
@@ -0,0 +1,83 @@
+#include <iostream>
+#include <string>
+
+struct DefaultSlotKey;
+
+template <class Type, class Key = DefaultSlotKey>
+class Slot
+{
+protected:
+    Type& doGet()
+    {
+        return value_;
+    }
+
+    void doSet(const Type& value)
+    {
+        value_ = value;
+    }
+
+    template <class... Args>
+    void doEmplace(Args&&... args)
+    {
+        value_ = Type(std::forward<Args>(args)...);
+    }
+private:
+    Type value_;
+};
+
+template <class... Slots>
+class Repository : private Slots...
+{
+public:
+    template <class Type, class Key = DefaultSlotKey>
+    Type& get()
+    {
+        static_assert(std::is_base_of<Slot<Type, Key>, Repository<Slots...>>::value,
+                      "Please ensure that this type or this key exists in this repository");
+        return Slot<Type, Key>::doGet();
+    }
+
+    template <class Type, class Key = DefaultSlotKey>
+    void set(const Type& value)
+    {
+        static_assert(std::is_base_of<Slot<Type, Key>, Repository<Slots...>>::value,
+                      "Please ensure that this type or this key exists in this repository");
+        Slot<Type, Key>::doSet(value);
+    }
+
+    template <class Type, class Key = DefaultSlotKey, class... Args>
+    void emplace(Args&&... args)
+    {
+        static_assert(std::is_base_of<Slot<Type, Key>, Repository<Slots...>>::value,
+                      "Please ensure that this type or this key exists in this repository");
+        Slot<Type, Key>::doEmplace(std::forward<Args>(args)...);
+    }
+};
+
+// Incomplete types used as compile-time keys.
+struct Key1;
+struct Key2;
+
+// Create a type for our repository.
+using MyRepository = Repository
+        <
+                Slot<int>,       // Let's pick the type of our slots.
+                Slot<std::string>
+        >;
+
+int main()
+{
+    MyRepository myRepository;
+
+    myRepository.set<std::string>("toto");
+    myRepository.set(42);
+
+    std::cout << myRepository.get<int>() << std::endl; // Print: "toto".
+    std::cout << myRepository.get<std::string>() << std::endl; // Print: 42.
+
+    myRepository.emplace<std::string>(4, 'a');
+    std::cout << myRepository.get<std::string>() << std::endl; // Print: 42.
+
+    return EXIT_SUCCESS;
+}