2
0
Fork 0
mirror of https://github.com/bevyengine/bevy synced 2024-12-24 12:03:14 +00:00
bevy/examples/ecs/system_piping.rs

73 lines
2.4 KiB
Rust
Raw Normal View History

//! Illustrates how to make a single system from multiple functions running in sequence,
//! passing the output of the first into the input of the next.
use bevy::prelude::*;
use std::num::ParseIntError;
use bevy::{
log::LogPlugin,
utils::{dbg, error, info, tracing::Level, warn},
};
fn main() {
App::new()
.insert_resource(Message("42".to_string()))
.insert_resource(OptionalWarning(Err("Got to rusty?".to_string())))
.add_plugins(LogPlugin {
level: Level::TRACE,
filter: "".to_string(),
..default()
})
.add_systems(
Update,
(
parse_message_system.pipe(handler_system),
Add `system.map(...)` for transforming the output of a system (#8526) # Objective Any time we wish to transform the output of a system, we currently use system piping to do so: ```rust my_system.pipe(|In(x)| do_something(x)) ``` Unfortunately, system piping is not a zero cost abstraction. Each call to `.pipe` requires allocating two extra access sets: one for the second system and one for the combined accesses of both systems. This also adds extra work to each call to `update_archetype_component_access`, which stacks as one adds multiple layers of system piping. ## Solution Add the `AdapterSystem` abstraction: similar to `CombinatorSystem`, this allows you to implement a trait to generically control how a system is run and how its inputs and outputs are processed. Unlike `CombinatorSystem`, this does not have any overhead when computing world accesses which makes it ideal for simple operations such as inverting or ignoring the output of a system. Add the extension method `.map(...)`: this is similar to `.pipe(...)`, only it accepts a closure as an argument instead of an `In<T>` system. ```rust my_system.map(do_something) ``` This has the added benefit of making system names less messy: a system that ignores its output will just be called `my_system`, instead of `Pipe(my_system, ignore)` --- ## Changelog TODO ## Migration Guide The `system_adapter` functions have been deprecated: use `.map` instead, which is a lightweight alternative to `.pipe`. ```rust // Before: my_system.pipe(system_adapter::ignore) my_system.pipe(system_adapter::unwrap) my_system.pipe(system_adapter::new(T::from)) // After: my_system.map(std::mem::drop) my_system.map(Result::unwrap) my_system.map(T::from) // Before: my_system.pipe(system_adapter::info) my_system.pipe(system_adapter::dbg) my_system.pipe(system_adapter::warn) my_system.pipe(system_adapter::error) // After: my_system.map(bevy_utils::info) my_system.map(bevy_utils::dbg) my_system.map(bevy_utils::warn) my_system.map(bevy_utils::error) ``` --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2023-08-28 16:36:46 +00:00
data_pipe_system.map(info),
parse_message_system.map(dbg),
warning_pipe_system.map(warn),
parse_error_message_system.map(error),
parse_message_system.map(drop),
),
)
.run();
}
Make `Resource` trait opt-in, requiring `#[derive(Resource)]` V2 (#5577) *This PR description is an edited copy of #5007, written by @alice-i-cecile.* # Objective Follow-up to https://github.com/bevyengine/bevy/pull/2254. The `Resource` trait currently has a blanket implementation for all types that meet its bounds. While ergonomic, this results in several drawbacks: * it is possible to make confusing, silent mistakes such as inserting a function pointer (Foo) rather than a value (Foo::Bar) as a resource * it is challenging to discover if a type is intended to be used as a resource * we cannot later add customization options (see the [RFC](https://github.com/bevyengine/rfcs/blob/main/rfcs/27-derive-component.md) for the equivalent choice for Component). * dependencies can use the same Rust type as a resource in invisibly conflicting ways * raw Rust types used as resources cannot preserve privacy appropriately, as anyone able to access that type can read and write to internal values * we cannot capture a definitive list of possible resources to display to users in an editor ## Notes to reviewers * Review this commit-by-commit; there's effectively no back-tracking and there's a lot of churn in some of these commits. *ira: My commits are not as well organized :')* * I've relaxed the bound on Local to Send + Sync + 'static: I don't think these concerns apply there, so this can keep things simple. Storing e.g. a u32 in a Local is fine, because there's a variable name attached explaining what it does. * I think this is a bad place for the Resource trait to live, but I've left it in place to make reviewing easier. IMO that's best tackled with https://github.com/bevyengine/bevy/issues/4981. ## Changelog `Resource` is no longer automatically implemented for all matching types. Instead, use the new `#[derive(Resource)]` macro. ## Migration Guide Add `#[derive(Resource)]` to all types you are using as a resource. If you are using a third party type as a resource, wrap it in a tuple struct to bypass orphan rules. Consider deriving `Deref` and `DerefMut` to improve ergonomics. `ClearColor` no longer implements `Component`. Using `ClearColor` as a component in 0.8 did nothing. Use the `ClearColorConfig` in the `Camera3d` and `Camera2d` components instead. Co-authored-by: Alice <alice.i.cecile@gmail.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: devil-ira <justthecooldude@gmail.com> Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-08-08 21:36:35 +00:00
#[derive(Resource, Deref)]
struct Message(String);
#[derive(Resource, Deref)]
struct OptionalWarning(Result<(), String>);
// This system produces a Result<usize> output by trying to parse the Message resource.
fn parse_message_system(message: Res<Message>) -> Result<usize, ParseIntError> {
message.parse::<usize>()
}
// This system produces a Result<()> output by trying to parse the Message resource.
fn parse_error_message_system(message: Res<Message>) -> Result<(), ParseIntError> {
message.parse::<usize>()?;
Ok(())
}
// This system takes a Result<usize> input and either prints the parsed value or the error message
// Try changing the Message resource to something that isn't an integer. You should see the error
// message printed.
fn handler_system(In(result): In<Result<usize, ParseIntError>>) {
match result {
Ok(value) => println!("parsed message: {value}"),
Err(err) => println!("encountered an error: {err:?}"),
}
}
// This system produces a String output by trying to clone the String from the Message resource.
fn data_pipe_system(message: Res<Message>) -> String {
message.0.clone()
}
// This system produces an Result<String> output by trying to extract a String from the
// OptionalWarning resource. Try changing the OptionalWarning resource to None. You should
// not see the warning message printed.
fn warning_pipe_system(message: Res<OptionalWarning>) -> Result<(), String> {
message.0.clone()
}