bevy/examples/ecs/system_chaining.rs
Carter Anderson 11b41206eb Add upstream bevy_ecs and prepare for custom-shaders merge (#2815)
This updates the `pipelined-rendering` branch to use the latest `bevy_ecs` from `main`. This accomplishes a couple of goals:

1. prepares for upcoming `custom-shaders` branch changes, which were what drove many of the recent bevy_ecs changes on `main`
2. prepares for the soon-to-happen merge of `pipelined-rendering` into `main`. By including bevy_ecs changes now, we make that merge simpler / easier to review. 

I split this up into 3 commits:

1. **add upstream bevy_ecs**: please don't bother reviewing this content. it has already received thorough review on `main` and is a literal copy/paste of the relevant folders (the old folders were deleted so the directories are literally exactly the same as `main`).
2. **support manual buffer application in stages**: this is used to enable the Extract step. we've already reviewed this once on the `pipelined-rendering` branch, but its worth looking at one more time in the new context of (1).
3. **support manual archetype updates in QueryState**: same situation as (2).
2021-09-14 06:14:19 +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),
}
}