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system_piping.rs
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system_piping.rs
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//! 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;
use bevy::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),
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();
}
#[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()
}