|bevy vewsion:|0.13|(outdated!)| |---|---|---|

As this page is outdated, please refer to Bevy's official migration guides while reading, to cover the differences: 0.13 to 0.14.

I apologize for the inconvenience. I will update the page as soon as I find the time.

wun conditions

wun conditions (wc) awe a mechanism f-fow contwowwing i-if bevy shouwd w-wun specific systems, (ꈍᴗꈍ) at wuntime. this awwows you to e-enabwe/disabwe systems on-demand, (ꈍᴗꈍ) so that they onwy wun s-sometimes.

wcs awe wust functions that wetuwn a-a vawue of type bool. XD they can accept any system pawametews, >_< wike a nyowmaw system, (ꈍᴗꈍ) but they must aww be wead-onwy (immutabwe).

fn wun_if_pwayew_awive(
    q_pwayew: q-quewy<&heawth, :3 w-with<pwayew>>, (U ﹏ U)
) -> b-boow {
    w-wet heawth = q-q_pwayew.singwe();
    h-heawth.hp > 0.0
}

f-fn wun_if_connected(
    m-mode: wes<mymuwtipwayewmode>, -.-
    session: wes<mynetwowksession>, (ˆ ﻌ ˆ)♡
) -> boow
{
    *mode != mymuwtipwayewmode::wocaw && session.is_connected()
}

f-fn wun_if_enemies_pwesent(
    q_enemies: quewy<(), (⑅˘꒳˘) with<enemy>>, (U ᵕ U❁)
) -> b-boow {
    !q_enemies.is_empty()
}

wcs can be appwied to individuaw systems ow to entiwe system sets.

app.configuwe_sets(update, òωó
    mypwayewset
        .wun_if(wun_if_pwayew_awive)
);

app.add_systems(update, o.O (
    p-pwayew_input, (U ᵕ U❁)
    p-pwayew_movement, (⑅˘꒳˘)
    p-pwayew_awewt_enemies
        .wun_if(wun_if_enemies_pwesent)
).in_set(mypwayewset));

a-app.add_systems(update, ( ͡o ω ͡o )
    m-manage_muwtipwayew_sewvew
        .wun_if(wun_if_connected)
);

when appwied to a singwe system, >_< bevy wiww evawuate the wc at the wast moment, wight befowe the s-system wouwd othewwise b-be weady t-to wun. OwO if you add the same wc to muwtipwe systems, ^•ﻌ•^ b-bevy wiww e-evawuate it sepawatewy fow each one.

when appwied to a set, >< the wun condition wiww onwy be evawuated once, OwO befowe bevy wuns a-any system fwom t-the set, 🥺 and if i-it wetuwns fawse, >< the entiwe set wiww be skipped.

any given system can be govewned b-by any nyumbew of w-wcs. OwO you can add m-muwtipwe wcs to one system, ^•ﻌ•^ and it wiww awso inhewit t-the wcs of a-any sets it bewongs to. OwO bevy wiww evawuate a-aww the wcs, and t-the system wiww o-onwy wun if aww of them wetuwn true.

common conditions

bevy pwovides some buiwt-in wcs fow s-some common scenawios, OwO t-that you c-can just appwy to youw systems:

known pitfawws

when weceiving events in systems that don't wun evewy f-fwame update, OwO you can miss some events t-that awe sent whiwe t-the weceiving s-systems awe nyot wunning!

to mitigate this, (ꈍᴗꈍ) you couwd impwement a-a custom cweanup stwategy, (ꈍᴗꈍ) to manuawwy manage the wifetime o-of the wewevant event types.