Properly link flecs library

engine/libs/flecs/examples/cpp/rules/component_inheritance/src/main.cpp

@@ -0,0 +1,58 @@
+#include <component_inheritance.h>
+#include <iostream>
+
+// This example shows how rules can be used to match simple inheritance trees.
+
+struct Unit { };
+struct CombatUnit : Unit { };
+struct MeleeUnit : CombatUnit { };
+struct RangedUnit : CombatUnit { };
+
+struct Warrior : MeleeUnit { };
+struct Wizard : RangedUnit { };
+struct Marksman : RangedUnit { };
+struct Builder : Unit { };
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    // Make the ECS aware of the inheritance relationships. Note that IsA
+    // relationship used here is the same as in the prefab example.
+    ecs.component<CombatUnit>().is_a<Unit>();
+    ecs.component<MeleeUnit>().is_a<CombatUnit>();
+    ecs.component<RangedUnit>().is_a<CombatUnit>();
+
+    ecs.component<Warrior>().is_a<MeleeUnit>();
+    ecs.component<Wizard>().is_a<RangedUnit>();
+    ecs.component<Marksman>().is_a<RangedUnit>();
+    ecs.component<Builder>().is_a<Unit>();
+
+    // Create a few units
+    ecs.entity("warrior_1").add<Warrior>();
+    ecs.entity("warrior_2").add<Warrior>();
+
+    ecs.entity("marksman_1").add<Marksman>();
+    ecs.entity("marksman_2").add<Marksman>();
+
+    ecs.entity("wizard_1").add<Wizard>();
+    ecs.entity("wizard_2").add<Wizard>();
+
+    ecs.entity("builder_1").add<Builder>();
+    ecs.entity("builder_2").add<Builder>();
+
+    // Create a rule to find all ranged units
+    flecs::rule<RangedUnit> r = ecs.rule<RangedUnit>();
+
+    // Iterate the rule
+    r.each([](flecs::entity e, RangedUnit) {
+        std::cout << "Unit " << e.name() << " found\n";
+    });
+
+    r.destruct();
+
+    // Output:
+    //   Unit wizard_1 found
+    //   Unit wizard_2 found
+    //   Unit marksman_1 found
+    //   Unit marksman_2 found
+}