figures: create function use city reference instead id

Author: dalerank

src/figuretype/figure_kingdome_trader.cpp

@@ -45,9 +45,9 @@ int figure::trader_total_sold() {
     return resource_amount_full;
 }
 
-int figure_create_trade_caravan(tile2i tile, int city_id) {
+int figure_trade_caravan::create(tile2i tile, const empire_city& city) {
     figure* caravan = figure_create(FIGURE_TRADE_CARAVAN, tile, DIR_0_TOP_RIGHT);
-    caravan->empire_city_id = city_id;
+    caravan->empire_city_id = city.name_id;
     caravan->action_state = FIGURE_ACTION_100_TRADE_CARAVAN_CREATED;
     caravan->wait_ticks = trade_caravan_m.wait_ticks_after_create;
     // donkey 1

src/figuretype/figure_kingdome_trader.h

@@ -2,7 +2,7 @@
 
 #include "figure_trader.h"
 
-int figure_create_trade_caravan(tile2i tile, int city_id);
+struct empire_city;
 
 class figure_trade_caravan : public figure_trader {
 public:
@@ -27,4 +27,5 @@ class figure_trade_caravan : public figure_trader {
     const static_params &current_params() const { static_cast<const static_params &>(params()); }
 
     void go_to_next_storageyard(tile2i src_tile, int distance_to_entry);
+    static int create(tile2i tile, const empire_city& city);
 };

src/figuretype/figure_trader_ship.cpp

@@ -30,9 +30,9 @@ void game_cheat_sink_all_ships(std::istream &is, std::ostream &os) {
     }, FIGURE_TRADE_SHIP, FIGURE_FISHING_BOAT);
 }
 
-int figure_trade_ship::create(tile2i tile, int city_id) {
+int figure_trade_ship::create(tile2i tile, const empire_city& city) {
     figure* ship = figure_create(FIGURE_TRADE_SHIP, tile, DIR_0_TOP_RIGHT);
-    ship->empire_city_id = city_id;
+    ship->empire_city_id = city.name_id;
     ship->allow_move_type = EMOVE_DEEPWATER;
     ship->action_state = FIGURE_ACTION_110_TRADE_SHIP_CREATED;
     ship->wait_ticks = 10;

src/figuretype/figure_trader_ship.h

@@ -9,6 +9,8 @@ enum {
     TRADE_SHIP_SELLING = 2,
 };
 
+struct empire_city;
+
 class figure_trade_ship : public figure_carrier {
 public:
     FIGURE_METAINFO(FIGURE_TRADE_SHIP, figure_trade_ship)
@@ -30,5 +32,5 @@ class figure_trade_ship : public figure_carrier {
     bool done_trading();
     int is_trading() const;
 
-    static int create(tile2i tile, int city_id);
+    static int create(tile2i tile, const empire_city& city);
 };