helpers: entity_filler and registry_filler

ecs.hpp

@@ -1156,6 +1156,45 @@ namespace ecs_hpp
     };
 }
 
+// -----------------------------------------------------------------------------
+//
+// fillers
+//
+// -----------------------------------------------------------------------------
+
+namespace ecs_hpp
+{
+    class entity_filler final {
+    public:
+        entity_filler(entity& entity) noexcept
+        : entity_(entity) {}
+
+        template < typename T, typename... Args >
+        entity_filler& component(Args&&... args) {
+            entity_.assign_component<T>(std::forward<Args>(args)...);
+            return *this;
+        }
+    private:
+        entity& entity_;
+    };
+
+    class registry_filler final {
+    public:
+        registry_filler(registry& registry) noexcept
+        : registry_(registry) {}
+
+        template < typename T, typename... Args >
+        registry_filler& system(priority_t priority, Args&&... args) {
+            registry_.add_system<T>(
+                priority,
+                std::forward<Args>(args)...);
+            return *this;
+        }
+    private:
+        registry& registry_;
+    };
+}
+
 // -----------------------------------------------------------------------------
 //
 // entity impl

ecs_tests.cpp

@@ -978,6 +978,45 @@ TEST_CASE("registry") {
             REQUIRE(i == 25);
         }
     }
+    SECTION("fillers") {
+        struct component_n {
+            int i = 0;
+            component_n(int ni) : i(ni) {}
+        };
+
+        class system_n : public ecs::system {
+        public:
+            system_n(int n) : n_(n) {}
+            void process(ecs::registry& owner) override {
+                owner.for_each_component<component_n>(
+                    [this](const ecs::const_entity&, component_n& c) noexcept {
+                        c.i += n_;
+                    });
+            }
+        private:
+            int n_;
+        };
+        {
+            ecs::registry w;
+            ecs::registry_filler(w)
+                .system<system_n>(0, 1)
+                .system<system_n>(0, 2);
+
+            ecs::entity e1 = w.create_entity();
+            ecs::entity_filler(e1)
+                .component<component_n>(0)
+                .component<component_n>(1);
+
+            ecs::entity e2 = w.create_entity();
+            ecs::entity_filler(e2)
+                .component<component_n>(2);
+
+            w.process_all_systems();
+
+            REQUIRE(e1.get_component<component_n>().i == 4);
+            REQUIRE(e2.get_component<component_n>().i == 5);
+        }
+    }
 }
 
 TEST_CASE("example") {