features and events instead system priorities

untests/ecs_readme.cpp

@@ -0,0 +1,121 @@
+/*******************************************************************************
+ * This file is part of the "https://github.com/blackmatov/ecs.hpp"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019, by Matvey Cherevko (blackmatov@gmail.com)
+ ******************************************************************************/
+
+#include <catch2/catch.hpp>
+
+#include <ecs.hpp/ecs.hpp>
+namespace ecs = ecs_hpp;
+
+#include <string>
+#include <iostream>
+
+TEST_CASE("example") {
+
+    // events
+
+    struct update_event {
+        float dt{};
+    };
+
+    struct render_event {
+        std::string camera;
+    };
+
+    // components
+
+    struct movable {};
+    struct disabled {};
+
+    struct sprite {
+        std::string name;
+    };
+
+    struct position {
+        float x{};
+        float y{};
+    };
+
+    struct velocity {
+        float x{};
+        float y{};
+    };
+
+    // systems
+
+    class gravity_system : public ecs::system<update_event> {
+    public:
+        gravity_system(float gravity)
+        : gravity_(gravity) {}
+
+        void process(ecs::registry& world, const update_event& evt) override {
+            world.for_each_component<velocity>(
+            [this, &evt](ecs::entity, velocity& vel) {
+                vel.x += gravity_ * evt.dt;
+                vel.y += gravity_ * evt.dt;
+            }, ecs::exists<movable>{} && !ecs::exists<disabled>{});
+        }
+    private:
+        float gravity_{};
+    };
+
+    class movement_system : public ecs::system<update_event> {
+    public:
+        void process(ecs::registry& world, const update_event& evt) override {
+            world.for_joined_components<position, velocity>(
+            [&evt](ecs::entity, position& pos, const velocity& vel) {
+                pos.x += vel.x * evt.dt;
+                pos.y += vel.y * evt.dt;
+            }, ecs::exists<movable>{} && !ecs::exists<disabled>{});
+        }
+    };
+
+    class render_system : public ecs::system<render_event> {
+    public:
+        void process(ecs::registry& world, const render_event& evt) override {
+            world.for_joined_components<sprite, position>(
+            [&evt](ecs::entity, const sprite& s, const position& p) {
+                std::cout << "Render sprite:" << std::endl;
+                std::cout << "--> pos: " << p.x << "," << p.y << std::endl;
+                std::cout << "--> sprite: " << s.name << std::endl;
+                std::cout << "--> camera: " << evt.camera << std::endl;
+            }, !ecs::exists<disabled>{});
+        }
+    };
+
+    // world
+
+    ecs::registry world;
+
+    struct physics_feature {};
+    world.assign_feature<physics_feature>()
+        .add_system<movement_system>()
+        .add_system<gravity_system>(9.8f);
+
+    struct rendering_feature {};
+    world.assign_feature<rendering_feature>()
+        .add_system<render_system>();
+
+    // entities
+
+    auto entity_one = world.create_entity();
+    ecs::entity_filler(entity_one)
+        .component<movable>()
+        .component<sprite>("ship")
+        .component<position>(4.f, 2.f)
+        .component<velocity>(10.f, 20.f);
+
+    auto entity_two = world.create_entity();
+    ecs::entity_filler(entity_two)
+        .component<movable>()
+        .component<sprite>("player")
+        .component<position>(4.f, 2.f)
+        .component<velocity>(10.f, 20.f);
+
+    // processing
+
+    world.process_event(update_event{0.1f});
+    world.process_event(render_event{"main"});
+}