Properly link flecs library

engine/libs/flecs/examples/c/rules/setting_variables/.gitignore

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+.bake_cache
+.DS_Store
+.vscode
+gcov
+bin

engine/libs/flecs/examples/c/rules/setting_variables/include/setting_variables.h

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+#ifndef SETTING_VARIABLES_H
+#define SETTING_VARIABLES_H
+
+/* This generated file contains includes for project dependencies */
+#include "setting_variables/bake_config.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+

engine/libs/flecs/examples/c/rules/setting_variables/include/setting_variables/bake_config.h

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+/*
+                                   )
+                                  (.)
+                                  .|.
+                                  | |
+                              _.--| |--._
+                           .-';  ;`-'& ; `&.
+                          \   &  ;    &   &_/
+                           |"""---...---"""|
+                           \ | | | | | | | /
+                            `---.|.|.|.---'
+
+ * This file is generated by bake.lang.c for your convenience. Headers of
+ * dependencies will automatically show up in this file. Include bake_config.h
+ * in your main project file. Do not edit! */
+
+#ifndef SETTING_VARIABLES_BAKE_CONFIG_H
+#define SETTING_VARIABLES_BAKE_CONFIG_H
+
+/* Headers of public dependencies */
+#include <flecs.h>
+
+#endif
+

engine/libs/flecs/examples/c/rules/setting_variables/project.json

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+{
+    "id": "setting_variables",
+    "type": "application",
+    "value": {
+        "use": [
+            "flecs"
+        ]
+    }
+}

engine/libs/flecs/examples/c/rules/setting_variables/src/main.c

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+#include <setting_variables.h>
+#include <stdio.h>
+
+// This example extends the component_inheritance example, and shows how
+// we can use a single rule to match units from different players and platoons
+// by setting query variables before we iterate.
+//
+// The units in this example belong to a platoon, with the platoons belonging
+// to a player.
+
+static const int PlayerCount = 100;
+static const int PlatoonsPerPlayer = 3;
+
+int main(int argc, char *argv[]) {
+    ecs_world_t *ecs = ecs_init_w_args(argc, argv);
+
+    // Unit datamodel - see component_inheritance example
+    ECS_TAG(ecs, Unit);
+    ECS_ENTITY(ecs, CombatUnit, (IsA, Unit));
+    ECS_ENTITY(ecs, MeleeUnit,  (IsA, CombatUnit));
+    ECS_ENTITY(ecs, RangedUnit, (IsA, CombatUnit));
+
+    ECS_ENTITY(ecs, Warrior,    (IsA, MeleeUnit));
+    ECS_ENTITY(ecs, Wizard,     (IsA, RangedUnit));
+    ECS_ENTITY(ecs, Marksman,   (IsA, RangedUnit));
+    ECS_ENTITY(ecs, Builder,    (IsA, Unit));
+
+    // Player/Platoon tags
+    ECS_TAG(ecs, Player);
+    ECS_TAG(ecs, Platoon);
+
+    // Populate store with players and platoons
+    for (int p = 0; p < PlayerCount; p ++) {
+        ecs_entity_t player;
+
+        // Give first player a name so we can look it up later
+        if (p == 0) {
+            player = ecs_new_entity(ecs, "MyPlayer");
+        } else {
+            player = ecs_new_id(ecs);
+        }
+
+        // Add player tag so we can query for all players if we want to
+        ecs_add(ecs, player, Player);
+
+        for (int pl = 0; pl < PlatoonsPerPlayer; pl ++) {
+            ecs_entity_t platoon = ecs_new_w_pair(ecs, Player, player);
+
+            // Add platoon tag so we can query for all platoons if we want to
+            ecs_add(ecs, platoon, Platoon);
+
+            // Add warriors, wizards and marksmen to the platoon
+            ecs_entity_t warrior = ecs_new(ecs, Warrior);
+            ecs_add_pair(ecs, warrior, Platoon, platoon);
+
+            ecs_entity_t marksman = ecs_new(ecs, Marksman);
+            ecs_add_pair(ecs, marksman, Platoon, platoon);
+
+            ecs_entity_t wizard = ecs_new(ecs, Wizard);
+            ecs_add_pair(ecs, wizard, Platoon, platoon);
+        }
+    }
+
+    // Create a rule to find all RangedUnits for a platoon/player. The 
+    // equivalent query in the query DSL would look like this:
+    //   (Platoon, $Platoon), Player($Platoon, $Player)
+    //
+    // The way to read how this query is evaluated is:
+    // - find all entities with (Platoon, *), store * in _Platoon
+    // - check if _Platoon has (Player, *), store * in _Player
+    ecs_rule_t *r = ecs_rule(ecs, {
+        .terms = {
+            { .first.id = RangedUnit },
+            {
+                .first.id = Platoon, 
+                .second = { .name = "Platoon", .flags = EcsIsVariable },
+            },
+            { 
+                .first.id = Player, 
+                .src = { .name = "Platoon", .flags = EcsIsVariable },
+                .second = { .name = "Player", .flags = EcsIsVariable },
+            }
+        }
+    });
+
+    // If we would iterate this rule it would return all ranged units for all
+    // platoons & for all players. We can limit the results to just a single
+    // platoon or a single player setting a variable beforehand. In this example
+    // we'll just find all platoons & ranged units for a single player.
+
+    int player_var = ecs_rule_find_var(r, "Player");
+    int platoon_var = ecs_rule_find_var(r, "Platoon");
+
+    // Iterate rule, limit the results to units of MyPlayer
+    ecs_iter_t it = ecs_rule_iter(ecs, r);
+    ecs_iter_set_var(&it, player_var, ecs_lookup(ecs, "MyPlayer"));
+
+    while (ecs_rule_next(&it)) {
+        ecs_entity_t player = ecs_iter_get_var(&it, player_var);
+        ecs_entity_t platoon = ecs_iter_get_var(&it, platoon_var);
+        char *platoon_str = ecs_get_fullpath(ecs, platoon);
+        char *class_str = ecs_id_str(ecs, ecs_field_id(&it, 1));
+
+        for (int i = 0; i < it.count; i ++) {
+            char *unit_str = ecs_get_fullpath(ecs, it.entities[i]);
+            printf("Unit %s of class %s in platoon %s for player %s\n", 
+                unit_str, class_str, platoon_str,
+                ecs_get_name(ecs, player));
+            ecs_os_free(unit_str);
+        }
+
+        ecs_os_free(class_str);
+        ecs_os_free(platoon_str);
+    }
+
+    ecs_rule_fini(r);
+
+    // Output
+    //  Unit 513 of class Wizard in platoon 510 for player MyPlayer
+    //  Unit 517 of class Wizard in platoon 514 for player MyPlayer
+    //  Unit 521 of class Wizard in platoon 518 for player MyPlayer
+    //  Unit 512 of class Marksman in platoon 510 for player MyPlayer
+    //  Unit 516 of class Marksman in platoon 514 for player MyPlayer
+    //  Unit 520 of class Marksman in platoon 518 for player MyPlayer
+
+    return ecs_fini(ecs);
+}