Can now mark json/components with std::optional and then they can be null/false to disable them.

assets/bosses.json

@@ -3,7 +3,7 @@
     "components": [
       {"_type": "BossFight",
         "background": "boss_fight_background",
-        "stage": "none",
+        "stage": false,
         "weapon_sound": "Sword_Hit_2"
       },
       {"_type": "Combat", "hp": 20, "max_hp": 20, "damage": 20, "dead": false},
@@ -16,7 +16,7 @@
     "components": [
       {"_type": "BossFight",
         "background": "devils_fingers_background",
-        "stage": "none",
+        "stage": false,
         "weapon_sound": "Sword_Hit_2"
       },
       {"_type": "Combat", "hp": 20, "max_hp": 20, "damage": 20, "dead": false},

boss_fight_ui.cpp

@@ -50,14 +50,14 @@ namespace gui {
 
   void BossFightUI::configure_background() {
     auto& boss = $world->get<components::BossFight>($boss_id);
-    $boss_has_stage = boss.stage != "none";
 
     $boss_background = textures::get(boss.background);
     $boss_background.sprite->setPosition({BOSS_VIEW_X, BOSS_VIEW_Y});
     $status.world().set_the<Background>({$status.$parser});
 
-    if($boss_has_stage) {
-      $boss_stage = textures::get(boss.stage);
+    if(boss.stage) {
+      $boss_has_stage = true;
+      $boss_stage = textures::get(*boss.stage);
       $boss_stage.sprite->setPosition({BOSS_VIEW_X, BOSS_VIEW_Y});
     }
   }

components.hpp

@@ -1,5 +1,4 @@
 #pragma once
-#include "components.hpp"
 #include "config.hpp"
 #include "constants.hpp"
 #include "dinkyecs.hpp"
@@ -7,15 +6,10 @@
 #include <SFML/Graphics/Rect.hpp>
 #include <SFML/System/Vector2.hpp>
 #include <functional>
-#include <nlohmann/json.hpp>
-#include <nlohmann/json_fwd.hpp>
+#include <optional>
 #include "easings.hpp"
+#include "json_mods.hpp"
 
-#define ENROLL_COMPONENT(COMPONENT, ...)                         \
-    NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(COMPONENT, __VA_ARGS__);  \
-    template <> struct NameOf<COMPONENT> {                       \
-      static constexpr const char *name = #COMPONENT;            \
-    };
 
 namespace components {
   using namespace nlohmann;
@@ -69,7 +63,7 @@ namespace components {
 
   struct BossFight {
     std::string background;
-    std::string stage;
+    std::optional<std::string> stage;
     std::string weapon_sound;
   };
 
@@ -126,8 +120,16 @@ namespace components {
     void step(sf::Vector2f& scale_out, sf::Vector2f& pos_out, sf::IntRect& rect_out);
   };
 
+  struct Player {
+    DinkyECS::Entity entity;
+  };
+
   template <typename T> struct NameOf;
 
+  using ReflFuncSignature = std::function<void(DinkyECS::World& world, DinkyECS::Entity ent, nlohmann::json &j)>;
+
+  using ComponentMap = std::unordered_map<std::string, ReflFuncSignature>;
+
   ENROLL_COMPONENT(Tile, display, foreground, background);
   ENROLL_COMPONENT(BossFight, background, stage, weapon_sound);
   ENROLL_COMPONENT(Sprite, name, width, height, scale);
@@ -144,12 +146,6 @@ namespace components {
       speed, easing, ease_rate, stationary);
   ENROLL_COMPONENT(Sound, attack, death);
 
-  using ReflFuncSignature = std::function<void(DinkyECS::World& world, DinkyECS::Entity ent, nlohmann::json &j)>;
-  using ComponentMap = std::unordered_map<std::string, ReflFuncSignature>;
-  struct Player {
-    DinkyECS::Entity entity;
-  };
-
   template<typename COMPONENT> COMPONENT convert(nlohmann::json &data) {
     COMPONENT result;
     from_json(data, result);

json_mods.hpp

@@ -0,0 +1,34 @@
+#pragma once
+#include <nlohmann/json.hpp>
+#include <nlohmann/json_fwd.hpp>
+#include <optional>
+
+#define ENROLL_COMPONENT(COMPONENT, ...)                         \
+    NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(COMPONENT, __VA_ARGS__);  \
+    template <> struct NameOf<COMPONENT> {                       \
+      static constexpr const char *name = #COMPONENT;            \
+    };
+
+// partial specialization (full specialization works too)
+namespace nlohmann {
+  template <typename T>
+    struct adl_serializer<std::optional<T>> {
+      static void to_json(json& j, const std::optional<T>& opt) {
+        if (opt == std::nullopt) {
+          j = nullptr;
+        } else {
+          j = *opt; // this will call adl_serializer<T>::to_json which will
+          // find the free function to_json in T's namespace!
+        }
+      }
+
+      static void from_json(const json& j, std::optional<T>& opt) {
+        if (j.is_null() || j == false) {
+          opt = std::nullopt;
+        } else {
+          opt = std::make_optional<T>(j.template get<T>());
+          // same as above, but with adl_serializer<T>::from_json
+        }
+      }
+    };
+}