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use bevy_utils::all_tuples;
use super::{
BuildableSystemParam, FunctionSystem, Local, Res, ResMut, Resource, SystemMeta, SystemParam,
SystemParamFunction, SystemState,
};
use crate::prelude::{FromWorld, Query, World};
use crate::query::{QueryData, QueryFilter};
/// Builder struct used to construct state for [`SystemParam`] passed to a system.
///
/// ```
/// # use bevy_ecs::prelude::*;
/// # use bevy_ecs_macros::SystemParam;
/// # use bevy_ecs::system::RunSystemOnce;
/// #
/// # #[derive(Component)]
/// # struct A;
/// #
/// # #[derive(Component)]
/// # struct B;
/// #
/// # #[derive(Resource)]
/// # struct R;
/// #
/// # #[derive(SystemParam)]
/// # struct MyParam;
/// #
/// # let mut world = World::new();
/// # world.insert_resource(R);
///
/// fn my_system(res: Res<R>, query: Query<&A>, param: MyParam) {
/// // ...
/// }
///
/// // Create a builder from the world, helper methods exist to add `SystemParam`,
/// // alternatively use `.param::<T>()` for any other `SystemParam` types.
/// let system = SystemBuilder::<()>::new(&mut world)
/// .resource::<R>()
/// .query::<&A>()
/// .param::<MyParam>()
/// .build(my_system);
///
/// // Parameters that the builder is initialised with will appear first in the arguments.
/// let system = SystemBuilder::<(Res<R>, Query<&A>)>::new(&mut world)
/// .param::<MyParam>()
/// .build(my_system);
///
/// // Parameters that implement `BuildableSystemParam` can use `.builder::<T>()` to build in place.
/// let system = SystemBuilder::<()>::new(&mut world)
/// .resource::<R>()
/// .builder::<Query<&A>>(|builder| { builder.with::<B>(); })
/// .param::<MyParam>()
/// .build(my_system);
///
/// world.run_system_once(system);
///```
pub struct SystemBuilder<'w, T: SystemParam = ()> {
pub(crate) meta: SystemMeta,
pub(crate) state: T::State,
pub(crate) world: &'w mut World,
}
impl<'w, T: SystemParam> SystemBuilder<'w, T> {
/// Construct a new builder with the default state for `T`
pub fn new(world: &'w mut World) -> Self {
let mut meta = SystemMeta::new::<T>();
Self {
state: T::init_state(world, &mut meta),
meta,
world,
}
}
/// Construct the a system with the built params
pub fn build<F, Marker>(self, func: F) -> FunctionSystem<Marker, F>
where
F: SystemParamFunction<Marker, Param = T>,
{
FunctionSystem::from_builder(self, func)
}
/// Return the constructed [`SystemState`]
pub fn state(self) -> SystemState<T> {
SystemState::from_builder(self)
}
}
macro_rules! impl_system_builder {
($($curr: ident),*) => {
impl<'w, $($curr: SystemParam,)*> SystemBuilder<'w, ($($curr,)*)> {
/// Add `T` as a parameter built from the world
pub fn param<T: SystemParam>(mut self) -> SystemBuilder<'w, ($($curr,)* T,)> {
#[allow(non_snake_case)]
let ($($curr,)*) = self.state;
SystemBuilder {
state: ($($curr,)* T::init_state(self.world, &mut self.meta),),
meta: self.meta,
world: self.world,
}
}
/// Helper method for reading a [`Resource`] as a param, equivalent to `.param::<Res<T>>()`
pub fn resource<T: Resource>(self) -> SystemBuilder<'w, ($($curr,)* Res<'static, T>,)> {
self.param::<Res<T>>()
}
/// Helper method for mutably accessing a [`Resource`] as a param, equivalent to `.param::<ResMut<T>>()`
pub fn resource_mut<T: Resource>(self) -> SystemBuilder<'w, ($($curr,)* ResMut<'static, T>,)> {
self.param::<ResMut<T>>()
}
/// Helper method for adding a [`Local`] as a param, equivalent to `.param::<Local<T>>()`
pub fn local<T: Send + FromWorld>(self) -> SystemBuilder<'w, ($($curr,)* Local<'static, T>,)> {
self.param::<Local<T>>()
}
/// Helper method for adding a [`Query`] as a param, equivalent to `.param::<Query<D>>()`
pub fn query<D: QueryData>(self) -> SystemBuilder<'w, ($($curr,)* Query<'static, 'static, D, ()>,)> {
self.query_filtered::<D, ()>()
}
/// Helper method for adding a filtered [`Query`] as a param, equivalent to `.param::<Query<D, F>>()`
pub fn query_filtered<D: QueryData, F: QueryFilter>(self) -> SystemBuilder<'w, ($($curr,)* Query<'static, 'static, D, F>,)> {
self.param::<Query<D, F>>()
}
/// Add `T` as a parameter built with the given function
pub fn builder<T: BuildableSystemParam>(
mut self,
func: impl FnOnce(&mut T::Builder<'_>),
) -> SystemBuilder<'w, ($($curr,)* T,)> {
#[allow(non_snake_case)]
let ($($curr,)*) = self.state;
SystemBuilder {
state: ($($curr,)* T::build(self.world, &mut self.meta, func),),
meta: self.meta,
world: self.world,
}
}
}
};
}
all_tuples!(impl_system_builder, 0, 15, P);
#[cfg(test)]
mod tests {
use crate as bevy_ecs;
use crate::prelude::{Component, Query};
use crate::system::{Local, RunSystemOnce};
use super::*;
#[derive(Component)]
struct A;
fn local_system(local: Local<u64>) -> u64 {
*local
}
fn query_system(query: Query<()>) -> usize {
query.iter().count()
}
fn multi_param_system(a: Local<u64>, b: Local<u64>) -> u64 {
*a + *b + 1
}
#[test]
fn local_builder() {
let mut world = World::new();
let system = SystemBuilder::<()>::new(&mut world)
.builder::<Local<u64>>(|x| *x = 10)
.build(local_system);
let result = world.run_system_once(system);
assert_eq!(result, 10);
}
#[test]
fn query_builder() {
let mut world = World::new();
world.spawn(A);
world.spawn_empty();
let system = SystemBuilder::<()>::new(&mut world)
.builder::<Query<()>>(|query| {
query.with::<A>();
})
.build(query_system);
let result = world.run_system_once(system);
assert_eq!(result, 1);
}
#[test]
fn multi_param_builder() {
let mut world = World::new();
world.spawn(A);
world.spawn_empty();
let system = SystemBuilder::<()>::new(&mut world)
.local::<u64>()
.param::<Local<u64>>()
.build(multi_param_system);
let result = world.run_system_once(system);
assert_eq!(result, 1);
}
}