Add example extending base Creep type to always have an ID

javascript/main.js

@@ -36,8 +36,10 @@ module.exports.loop = function () {
         Game.cpu.halt();
     } else {
         try {
+            // Capture current list of creeps
+            const creeps = Object.values(Game.creeps);
             if (wasm_module) {
-                wasm_module.loop();
+                wasm_module.loop(creeps);
             } else {
                 // attempt to load the wasm only if there's enough bucket to do a bunch of work this tick
                 if (Game.cpu.bucket < 750) {
@@ -49,7 +51,7 @@ module.exports.loop = function () {
                 // load the wasm instance!
                 wasm_module.initialize_instance();
                 // go ahead and run the loop for its first tick
-                wasm_module.loop();
+                wasm_module.loop(creeps);
             }
         } catch (error) {
             console.error("caught exception:", error);

src/lib.rs

@@ -3,19 +3,21 @@ use std::{
     collections::{hash_map::Entry, HashMap, HashSet},
 };
 
+use crate::types::Creep;
 use js_sys::{JsString, Object, Reflect};
 use log::*;
 use screeps::{
     constants::{ErrorCode, Part, ResourceType},
     enums::StructureObject,
     find, game,
     local::ObjectId,
-    objects::{Creep, Source, StructureController},
+    objects::{Source, StructureController},
     prelude::*,
 };
 use wasm_bindgen::{prelude::*, JsCast};
 
 mod logging;
+mod types;
 
 // this is one way to persist data between ticks within Rust's memory, as opposed to
 // keeping state in memory on game objects - but will be lost on global resets!
@@ -35,9 +37,12 @@ enum CreepTarget {
 }
 
 // add wasm_bindgen to any function you would like to expose for call from js
-// to use a reserved name as a function name, use `js_name`:
+// to use a reserved name as a function name, use `js_name`.
+// You can pass arguments from JS. For example, here we are passing in the list of creeps
+// as of the start of the tick and since we know we haven't spawned any creeps yet this tick
+// we can use our custom Creep type instead of screeps::Creep.
 #[wasm_bindgen(js_name = loop)]
-pub fn game_loop() {
+pub fn game_loop(creeps: Vec<Creep>) {
     INIT_LOGGING.call_once(|| {
         // show all output of Info level, adjust as needed
         logging::setup_logging(logging::Info);
@@ -50,7 +55,7 @@ pub fn game_loop() {
     CREEP_TARGETS.with(|creep_targets_refcell| {
         let mut creep_targets = creep_targets_refcell.borrow_mut();
         debug!("running creeps");
-        for creep in game::creeps().values() {
+        for creep in creeps {
             run_creep(&creep, &mut creep_targets);
         }
     });

src/types.rs

@@ -0,0 +1,29 @@
+use js_sys::JsString;
+use screeps::HasId;
+use wasm_bindgen::prelude::wasm_bindgen;
+
+// The Rust mappings of the JS Types can be extended to modify their functionality.
+// Here, we create a custom Creep type we can use when we know what a Creep definitely has an ID.
+// Each tick, JS will pass in a list of Creeps which we will convert to this custom type since
+// the only way a creep could *not* have an ID is if it was just spawned this tick, and by passing
+// in the creeps from JS before our bot code runs, we know that we have not spawned any new creeps yet
+#[wasm_bindgen]
+extern "C" {
+    // By specifying `extends`, wasm_bindgen will implement Deref for the base type,
+    // thus anything a screeps::Creep can do, so can our custom type
+    #[wasm_bindgen(extends = screeps::Creep)]
+    pub type Creep;
+
+    // Define our own id_internal method instead of screeps::Creep::id_internal since we
+    // know that Creeps represented by this type always have an ID
+    #[wasm_bindgen(method, getter = id)]
+    fn id_internal(this: &Creep) -> JsString;
+}
+
+// Implement HasId for our custom creep type (instead of MaybeHasId) since this type is used
+// for creeps that are known to have an ID.
+impl HasId for Creep {
+    fn js_raw_id(&self) -> JsString {
+        self.id_internal()
+    }
+}