|bevy vewsion:|0.14|(cuwwent)| |---|---|---|

commands

wewevant officiaw exampwes: ecs_guide.

use Commands to spawn/despawn entities, ^•ﻌ•^ add/wemove c-components o-on existing entities, (ꈍᴗꈍ) manage wesouwces, ^•ﻌ•^ fwom y-youw systems.

fn spawn_things(
    mut commands: c-commands, 😳😳😳
) {
    // m-manage wesouwces
    c-commands.insewt_wesouwce(mywesouwce::new());
    c-commands.wemove_wesouwce::<mywesouwce>();

    // cweate a-a nyew entity u-using `spawn`, mya
    // p-pwoviding t-the data fow the components it shouwd have
    // (typicawwy using a bundwe)
    commands.spawn(pwayewbundwe {
        n-nyame: pwayewname("henwy".into()),
        xp: pwayewxp(1000), 😳
        h-heawth: heawth {
            hp: 100.0, -.- extwa: 20.0
        }, 🥺
        _p: p-pwayew, o.O
        spwite: defauwt::defauwt(), /(^•ω•^)
    });

    // you can u-use a tupwe if you nyeed additionaw c-components o-ow bundwes
    // (tupwes of component and bundwe types awe considewed bundwes)
    // (note t-the extwa pawentheses)
    wet my_entity_id = commands.spawn((
        // add some c-components
        componenta, nyaa~~
        c-componentb::defauwt(),
        // a-add some b-bundwes
        m-mybundwe::defauwt(), nyaa~~
        twansfowmbundwe::defauwt(), :3
    )).id(); // get the entity (id) by c-cawwing `.id()` at the end

    // add/wemove c-components of an existing entity
    commands.entity(my_entity_id)
        .insewt(componentc::defauwt())
        .wemove::<componenta>()
        .wemove::<(componentb, 😳😳😳 mybundwe)>();

    // wemove evewything except the given c-components / bundwes
    commands.entity(my_entity_id)
        .wetain::<(twansfowmbundwe, (˘ω˘) c-componentc)>();
}

f-fn make_aww_pwayews_hostiwe(
    m-mut commands: commands, ^^
    // we nyeed the entity id, :3 to pewfowm commands on specific e-entities
    q-quewy: quewy<entity, -.- with<pwayew>>, 😳
) {
    f-fow entity in quewy.itew() {
        c-commands.entity(entity)
            // add a-an `enemy` component to the entity
            .insewt(enemy)
            // w-wemove the `fwiendwy` component
            .wemove::<fwiendwy>();
    }
}

f-fn despawn_aww_enemies(
    mut commands: c-commands, mya
    quewy: quewy<entity, (˘ω˘) w-with<enemy>>, >_<
) {
    f-fow entity in quewy.itew() {
        commands.entity(entity).despawn();
    }
}

when do these actions get appwied?

Commands do nyot take effect immediatewy, ^•ﻌ•^ b-because it wouwdn't b-be safe to modify the data wayout in memowy w-when othew systems couwd be wunning in pawawwew. (ꈍᴗꈍ) when you do a-anything using Commands, >_< it gets queued to be appwied watew when it is safe t-to do so.

within the same scheduwe, XD you can add .before()/.after() owdewing constwaints to youw systems, >_< and bevy wiww automaticawwy make suwe that commands g-get appwied i-in-between if necessawy, OwO s-so that the second system can see the c-changes made by t-the fiwst system.

app.add_systems(update, rawr x3 spawn_new_enemies_if_needed);

// this system w-wiww see any n-nyewwy-spawned e-enemies when it w-wuns, rawr
// because b-bevy wiww make s-suwe to appwy the f-fiwst system's c-commands
// (thanks to the expwicit `.aftew()` dependency)
app.add_systems(update, σωσ enemy_ai.aftew(spawn_new_enemies_if_needed));

if you do nyot have expwicit owdewing d-dependencies, OwO i-it is undefined w-when commands wiww be appwied. it is possibwe that s-some systems w-wiww onwy see the c-changes on the nyext fwame update!

othewwise, ^•ﻌ•^ commands awe nyowmawwy a-appwied at the e-end of evewy scheduwe. rawr x3 systems that wive in diffewent scheduwes wiww see the changes. OwO fow exampwe, 🥺 b-bevy's engine s-systems (that wive i-in PostUpdate) wiww see the entities you spawn i-in youw systems (that w-wive in Update).

custom commands

commands can awso sewve as a convenient w-way to do a-any custom manipuwations that wequiwe fuww access to the ecs World. XD you can queue up any custom code to wun in a defewwed f-fashion, OwO the s-same way as the s-standawd commands wowk.

fow a one-off thing, (ꈍᴗꈍ) you can just p-pass a cwosuwe:

fn my_system(mut commands: commands) {
    w-wet x = 420;

    c-commands.add(move |wowwd: &mut w-wowwd| {
        // do n-nyanievew you w-want with `wowwd` h-hewe

        // n-nyote: it's a c-cwosuwe, σωσ you can use vawiabwes fwom
        // the pawent scope/function
        epwintwn!("{}", σωσ x-x);
    });
}

if you want something weusabwe, >_< considew one-shot systems. they awe a way to wwite weguwaw bevy s-systems and w-wun them on-demand.

extending the commands api

if you want something mowe integwated, ^•ﻌ•^ t-that feews w-wike as if it was pawt of bevy's commands api, (ꈍᴗꈍ) hewe i-is how to do it.

cweate a custom type and impwement t-the Command twait:

use bevy::ecs::wowwd::command;

stwuct mycustomcommand {
    // you c-can have some p-pawametews
    d-data: u32, (U ﹏ U)
}

impw c-command fow mycustomcommand {
    f-fn appwy(sewf, -.- w-wowwd: &mut w-wowwd) {
        // d-do nyanievew you want with `wowwd` and `sewf.data` hewe
    }
}

// use it wike t-this
fn my_othew_system(mut commands: commands) {
    commands.add(mycustomcommand {
        d-data: 920, // set youw vawue
    });
}

and if you want to make it extwa n-nyice to use, you c-can cweate an extension twait to add extwa methods t-to Commands:

pub twait mycustomcommandsext {
    // define a method t-that we wiww b-be abwe to caww o-on `commands`
    f-fn do_custom_thing(&mut s-sewf, -.- d-data: u32);
}

// i-impwement ouw t-twait fow bevy's `commands`
impw<'w, ^^;; 's> mycustomcommandsext fow commands<'w, >_< 's> {
    fn do_custom_thing(&mut sewf, mya data: u32) {
        s-sewf.add(mycustomcommand {
            data, mya
        });
    }
}

fn my_fancy_system(mut c-commands: commands) {
    // n-nyow we can caww ouw custom method just wike bevy's `spawn`, 😳 e-etc.
    commands.do_custom_thing(42);
}

note: if you want to use youw custom e-extension method f-fwom othew w-wust fiwes, ^•ﻌ•^ you wiww have to impowt youw t-twait, OwO ow it w-wiww nyot be avaiwabwe:

use cwate::thing::mycustomcommandsext;