Jiwan · November 3, 2018 05:49 · Oct 30, 2015 · Oct 30, 2015
diff --git a/main.cpp b/main.cpp
@@ -47,13 +47,18 @@ struct E
     Functor serialize;
 };
 
+// Primary template, inherit from std::false_type.
+// ::value will return false.
+// Note: the second unused template parameter is set to default as std::string!!!
 template <typename T, typename = std::string>
 struct hasSerialize
         : std::false_type
 {
 
 };
 
+// Partial template specialisation, inherit from std::true_type.
+// ::value will return true.
 template <typename T>
 struct hasSerialize<T, decltype(std::declval<T>().serialize())>
         : std::true_type

diff --git a/main.cpp b/main.cpp
@@ -0,0 +1,88 @@
+#include <iostream>
+
+struct A {};
+
+std::string to_string(const A&)
+{
+    return "I am a A!";
+}
+
+// Type B with a serialize method.
+struct B
+{
+    std::string serialize() const
+    {
+        return "I am a B!";
+    }
+};
+
+// Type C with a "wrong" serialize member (not a method) and a to_string overload.
+struct C
+{
+    std::string serialize;
+};
+
+std::string to_string(const C&)
+{
+    return "I am a C!";
+}
+
+struct D : A
+{
+    std::string serialize() const
+    {
+        return "I am a D!";
+    }
+};
+
+struct E
+{
+    struct Functor
+    {
+        std::string operator()(){
+            return "I am a E!";
+        }
+    };
+
+    Functor serialize;
+};
+
+template <typename T, typename = std::string>
+struct hasSerialize
+        : std::false_type
+{
+
+};
+
+template <typename T>
+struct hasSerialize<T, decltype(std::declval<T>().serialize())>
+        : std::true_type
+{
+
+};
+
+template <typename T> typename std::enable_if<hasSerialize<T>::value, std::string>::type serialize(T& obj)
+{
+    return obj.serialize();
+}
+
+template <typename T> typename std::enable_if<!hasSerialize<T>::value, std::string>::type serialize(T& obj)
+{
+    return to_string(obj);
+}
+
+int main() {
+    A a;
+    B b;
+    C c;
+    D d;
+    E e;
+
+    std::cout << serialize(a) << std::endl;
+    std::cout << serialize(b) << std::endl;
+    std::cout << serialize(c) << std::endl;
+    std::cout << serialize(d) << std::endl;
+    std::cout << serialize(e) << std::endl;
+
+    return 0;
+}