refactor: fix json_interface

include/dpp/ban.h

@@ -39,7 +39,7 @@ class DPP_EXPORT ban : public json_interface<ban> {
 	std::string reason;
 	/** User ID the ban applies to */
 	snowflake user_id;
-	
+
 	/** Constructor */
 	ban();
 
@@ -50,15 +50,7 @@ class DPP_EXPORT ban : public json_interface<ban> {
 	 * @param j A json object to read from
 	 * @return A reference to self
 	 */
-	 ban& fill_from_json(nlohmann::json* j);
-
-	/**
-	 * @brief Build json representation of a ban
-	 * @param with_id Include ID in json
-	 * 
-	 * @return std::string stringified json
-	 */
-	std::string build_json(bool with_id = false) const;
+	ban& fill_from_json(nlohmann::json* j);
 };
 
 /**

include/dpp/emoji.h

@@ -139,7 +139,7 @@ class DPP_EXPORT emoji : public managed, public json_interface<emoji>  {
 	 * @param with_id include the id in the JSON
 	 * @return std::string json data
 	 */
-	std::string build_json(bool with_id = false) const override;
+	std::string build_json(bool with_id = false) const;
 
 	/**
 	 * @brief Emoji requires colons

include/dpp/json_interface.h

@@ -32,30 +32,62 @@ namespace dpp {
 	 * 
 	 * @tparam T Type of class that implements the interface
 	 */
-	template<typename T> struct DPP_EXPORT json_interface {
+	template<typename T>
+	struct DPP_EXPORT json_interface {
 	protected:
-		/* Must not destruct through pointer to json_interface. */
+		/**
+		 * @brief Destructor is protected - cannot delete json_interface from outside
+		 *
+		 * Because we declare this, we have to declare all the other special members
+		 */
 		~json_interface() = default;
 
 	public:
 		/**
-		 * @brief Convert object from nlohmann::json
-		 * 
-		 * @param j nlohmann::json object
-		 * @return T& Reference to self for fluent calling
+		 * @brief Default constructor
 		 */
-		T& fill_from_json([[maybe_unused]] nlohmann::json* j) {
-			throw dpp::logic_exception("JSON interface doesn't implement parse_from_json");
-		}
+		constexpr json_interface() noexcept = default;
+
+		/**
+		 * @brief Copy constructor
+		 */
+		constexpr json_interface(const json_interface&) noexcept = default;
+
+		/**
+		 * @brief Move constructor
+		 */
+		constexpr json_interface(json_interface&&) noexcept = default;
 
 		/**
-		 * @brief Build JSON string from the object
-		 * 
-		 * @param with_id Include the ID in the JSON
-		 * @return std::string JSON string version of object
+		 * @brief Copy assignment operator
 		 */
-		virtual std::string build_json([[maybe_unused]] bool with_id = false) const {
-			throw dpp::logic_exception("JSON interface doesn't implement build_json");
+		constexpr json_interface &operator=(const json_interface&) noexcept = default;
+
+		/**
+		 * @brief Move assignment operator
+		 */
+		constexpr json_interface &operator=(json_interface&&) noexcept = default;
+
+		/**
+			* @brief Convert object from nlohmann::json
+			*
+			* @param j nlohmann::json object
+			* @return T& Reference to self for fluent calling
+			*/
+		template <typename U = T, typename = decltype(U::fill_from_json)>
+		T& fill_from_json(nlohmann::json* j) {
+			return static_cast<T*>(this)->fill_from_json(j);
+		}
+
+		/**
+			* @brief Convert object from nlohmann::json
+			*
+			* @param j nlohmann::json object
+			* @return T& Reference to self for fluent calling
+			*/
+		template <typename U = T, typename = decltype(U::build_json)>
+		std::string build_json(bool with_id = false) const {
+			return static_cast<const T*>(this)->build_json(with_id);
 		}
 	};
 } // namespace dpp

src/dpp/ban.cpp

@@ -40,10 +40,5 @@ ban& ban::fill_from_json(nlohmann::json* j) {
 	return *this;
 }
 
-std::string ban::build_json(bool with_id) const {
-	/* This is an unused stub, because sending a ban is simple as a user id and a reason */
-	return "{}";
-}
-
 } // namespace dpp