Properly link flecs library

engine/libs/flecs/examples/cpp/entities/hooks/src/main.cpp

@@ -0,0 +1,108 @@
+#include <hooks.h>
+#include <iostream>
+
+// Component hooks are callbacks that can be registered for a type that are
+// invoked during different parts of the component lifecycle.
+//
+// In the C++ API the ctor, dtor, copy and move methods of a type are 
+// automatically registered as component hooks.
+
+struct String {
+    String(const char *v = nullptr) {
+        flecs::log::trace("Ctor(const char*)");
+        value = ecs_os_strdup(v);
+    }
+
+    ~String() {
+        flecs::log::trace("Dtor");
+        ecs_os_free(value);
+    }
+
+    String(const String& obj) {
+        flecs::log::trace("Copy");
+        value = ecs_os_strdup(obj.value);
+    }
+
+    String(String&& obj) {
+        flecs::log::trace("Move");
+        value = obj.value;
+        obj.value = nullptr;
+    }
+
+    String& operator=(const String& obj) {
+        flecs::log::trace("Copy assign");
+        ecs_os_free(value);
+        value = ecs_os_strdup(obj.value);
+        return *this;
+    }
+
+    String& operator=(String&& obj) {
+        flecs::log::trace("Move assign");
+        ecs_os_free(value);
+        value = obj.value;
+        obj.value = nullptr;
+        return *this;
+    }
+
+    char *value;
+};
+
+struct Tag { };
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    // Register additional add, remove and set hooks for type
+    ecs.component<String>()
+        .on_add([](flecs::entity e, String&) {
+            flecs::log::trace("OnAdd: %s", e.name().c_str());
+        })
+        .on_remove([](flecs::entity e, String&) {
+            flecs::log::trace("OnRemove: %s", e.name().c_str());
+        })
+        .on_set([](flecs::entity e, String&) {
+            flecs::log::trace("OnSet: %s", e.name().c_str());
+        });
+
+    // Register in advance to keep output trace clean
+    ecs.component<Tag>();
+
+    flecs::log::set_level(0);
+
+    flecs::entity e = ecs.entity("Entity");
+
+    flecs::log::push("e.add<String>()");
+    e.add<String>();
+    flecs::log::pop();
+
+    flecs::log::push("e.set<String>({\"Hello World\"})");
+    e.set<String>({"Hello World"});
+    flecs::log::pop();
+
+    // This operation changes the entity's archetype, which invokes a move
+    flecs::log::push("e.add<Tag>()");
+    e.add<Tag>();
+    flecs::log::pop();
+
+    flecs::log::push("e.destruct()");
+    e.destruct();
+    flecs::log::pop();
+
+    flecs::log::set_level(-1);
+
+    // Output:
+    //  info: e.add<String>()
+    //  info: | Ctor
+    //  info: | OnAdd: Entity
+    //  info: e.set<String>({"Hello World"})
+    //  info: | Ctor
+    //  info: | Move assign
+    //  info: | OnSet: Entity
+    //  info: | Dtor
+    //  info: e.add<Tag>()
+    //  info: | Move
+    //  info: | Dtor
+    //  info: e.destruct()
+    //  info: | OnRemove: Entity
+    //  info: | Dtor
+}