bevy/examples/ecs/system_chaining.rs
François b724a0f586 Down with the system! (#2496)
# Objective

- Remove all the `.system()` possible.
- Check for remaining missing cases.

## Solution

- Remove all `.system()`, fix compile errors
- 32 calls to `.system()` remains, mostly internals, the few others should be removed after #2446
2021-07-27 23:42:36 +00:00

26 lines
842 B
Rust

use anyhow::Result;
use bevy::prelude::*;
fn main() {
App::new()
.insert_resource(Message("42".to_string()))
.add_system(parse_message_system.chain(handler_system))
.run();
}
struct Message(String);
// this system produces a Result<usize> output by trying to parse the Message resource
fn parse_message_system(message: Res<Message>) -> Result<usize> {
Ok(message.0.parse::<usize>()?)
}
// 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>>) {
match result {
Ok(value) => println!("parsed message: {}", value),
Err(err) => println!("encountered an error: {:?}", err),
}
}