Adding Monsters

Hands-on Rust — by Herbert Wolverson (56 / 120)

👈 Managing Complexity with Systems | TOC | Collision Detection 👉

Monsters have a lot in common with the player. They have a position and render information. They aren’t keyboard controlled and they shouldn’t have a Player tag. Instead, monsters need an Enemy tag component. Open components.rs, and add an Enemy tag:

EntitiesComponentsAndSystems/dungeonecs/src/components.rs

​ ​#​[​derive​(Clone, Copy, Debug, PartialEq)]
​ ​pub​ ​struct​ Enemy;

An empty structure is all that’s required for a tag class. You still need a way to spawn monsters. Open spawner.rs, and add a spawn_monster function. It’s very similar to the player spawning code:

EntitiesComponentsAndSystems/dungeonecs/src/spawner.rs

​ ​pub​ ​fn​ ​spawn_monster​(
​     ecs: &​mut​ World,
​     rng: &​mut​ RandomNumberGenerator,
​     pos : Point
​ ) {
​     ecs​.push​(
​         (Enemy,
​             pos,
​             Render{
​                 color: ​ColorPair​::​new​(WHITE, BLACK),
​                 glyph : ​match​ rng​.range​(0,4) {
​                     0 ​=>​ ​to_cp437​(​'E'​),
​                     1 ​=>​ ​to_cp437​(​'O'​),
​                     2 ​=>​ ​to_cp437​(​'o'​),
​                     _ ​=>​ ​to_cp437​(​'g'​),
​                 }
​             }
​         )
​     );
​ }

To spice things up a bit, the spawning code randomly selects one of four monster types…