Added test application for std::enable_if in convert struct.

test_app/main.cpp

@@ -0,0 +1,86 @@
+// Compile with "g++ main.cpp -lyaml-cpp --std=c++14"
+#include <yaml-cpp/yaml.h>
+
+#include <iostream>
+#include <memory>
+#include <type_traits>
+
+// Base class
+class A
+{
+public:
+	A() : a(-1) {}
+	A(int a) : a(a) {}
+
+	// virtual load/emit methods
+	virtual void load(const YAML::Node &node)
+	{
+		a = node["a"].as<decltype(a)>();
+	}
+	virtual YAML::Node emit() const
+	{
+		YAML::Node node;
+		node["a"] = a;
+		return node;
+	}
+	int a;
+};
+
+// Derived class
+class B : public A
+{
+public:
+	B() : b(-1) {}
+	B(int a, int b) : A(a), b(b) {}
+
+	// override virtual load/emit methods
+	virtual void load(const YAML::Node &node) override
+	{
+		A::load(node);
+		b = node["b"].as<decltype(b)>();
+	}
+	virtual YAML::Node emit() const override
+	{
+		YAML::Node node = A::emit();
+		node["b"] = b;
+		return node;
+	}
+	int b;
+};
+
+// Implementation of convert::{encode,decode} for all classes derived from or being A
+namespace YAML {
+	template<typename T> struct convert<T, typename std::enable_if<std::is_base_of<A, T>::value>::type>
+	{
+		static Node encode(const T &rhs)
+		{
+			Node node = rhs.emit();
+			return node;
+		}
+		static bool decode(const Node &node, T &rhs)
+		{
+			try {
+				rhs.load(node);
+			} catch(...) {
+				return false;
+			}
+			return true;
+		}
+	};
+}
+
+int main(int argc, char **argv)
+{
+	{ // Polymorphic emit
+		std::unique_ptr<A> base_ptr = std::make_unique<B>(1, 2);
+		YAML::Node node;
+		node.push_back(*base_ptr);
+		std::cout << YAML::Dump(node) << std::endl;
+	}
+	{ // load
+		std::unique_ptr<B> derived_ptr = std::make_unique<B>(1, 2);
+		*derived_ptr = YAML::Load("a: 3\nb: 4").as<B>();
+		std::cout << "a: " << derived_ptr->a << " b: " << derived_ptr->b << std::endl;
+	}
+	return 0;
+}