//! 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), 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() }