I want to query for entities with a given component, I then want to loop through these entities and do stuff to them based on their other components. Is there a way to then loop through or check for various components after the initial query?
#How can I get a list of Components for a given Entity?
lament solstice
outer smelt
Do you just need their info? If so you can add &Components to your system and use https://docs.rs/bevy/latest/bevy/ecs/component/struct.Components.html#method.iter
lament solstice
@outer smelt I can't get any of my queries to work, could you give me an example with &Components?
Or are you saying to use world: &mut World, parameter with .components()?
It's not clear to me how something world.components().component_id::<SomeCompA>() relates to specific entity in a Query.
outer smelt
Oh hm, I think I'm misremembering
I was thinking about something like this: https://github.com/bevyengine/bevy/discussions/3332#discussioncomment-1809893
But there's probably a better way nowadays
outer smelt
Oh wait yeah I marked that as the answer even lol
That should get you a Vec of ComponentInfo
lament solstice
world.inspect_entity(ent) this is probably good for me.. just didn't know it existed
thanks for working with me to find this.
outer smelt
No problem!
lament solstice
hmm.. i still can't figure out how to use world.. lol.. either getting a &World conflicts with a previous mutable system parameter. Allowing this would break Rust's mutability rules by putting it in the system params of the fn or I'm calling doing a let world = World::new(); in the fn but then after trying to use it, I'll get errors like Entity 2446v0 does not exist
pine swallow
The world contains all the entity data and resources, so you can't reference it immutably while also referencing one of its inner parts mutably
Just make your system take only an &mut World instead, you can access any resources or components you need through the world directly
surreal yew
Or use a paramset right?
pine swallow
That works yeah :p I've never used them personally so I kinda forgot lol
jagged light
I want to query for entities with a given component, I then want to loop through...
You might consider using something like
fn my_system(
query: Query<&ComponentA, Option<&ComponentB>, Option<&ComponentC>>
) {
// ...
}
instead
lament solstice
@surreal yew i would need a very complicated/long param set. the limit for param sets is 7 or 8 queries and I don't know how to nest them. .. so i didn't consider this route.
lament solstice
You might consider using something like
```rust
fn my_system(
query: Query<&C...
so if I combine an Entity in with this query I just can mark like 20 components as optional and then in the system I just check for None or Some on each entity within a loop?
jagged light
so if I combine an Entity in with this query I just can mark like 20 components ...
Yep
jagged light
You could also consider refactoring into multiple systems
fn sword_system(
swords: Query<(Entity, &Stats), With<Sword>>,
) {
// ...
}
fn rifle_system(
rifles: Query<(Entity, &Stats), With<Rifle>>,
) {
// ...
}
that would overly complicate how many systems i would need .. im using your approach.. with a match statement
outer smelt
You could also consider the Has query param instead of Option if all you need to know about is the component’s existence
lament solstice
i.e.
for-loop {
match (compA, compB, compC, compD, compE, compF, compG)
(Some(_), _, _, _, _, _, _,)
.. .. .
.. ..
}
like this^
lament solstice
https://docs.rs/bevy/latest/bevy/ecs/prelude/struct.Has.html
I've tried using Has in the past.. i never found it to work ..
or at least the way I would expect it to work
and still don't understand how that's different than With<Comp>
just simplifies the disjoint query thing?
outer smelt
It's more like Option<&T> than With<T>