bevy/examples/app/custom_loop.rs
Brezak de875fdc4c
Make AppExit more specific about exit reason. (#13022)
# Objective

Closes #13017.

## Solution

- Make `AppExit` a enum with a `Success` and `Error` variant.
- Make `App::run()` return a `AppExit` if it ever returns.
- Make app runners return a `AppExit` to signal if they encountered a
error.

---

## Changelog

### Added

- [`App::should_exit`](https://example.org/)
- [`AppExit`](https://docs.rs/bevy/latest/bevy/app/struct.AppExit.html)
to the `bevy` and `bevy_app` preludes,

### Changed

- [`AppExit`](https://docs.rs/bevy/latest/bevy/app/struct.AppExit.html)
is now a enum with 2 variants (`Success` and `Error`).
- The app's [runner
function](https://docs.rs/bevy/latest/bevy/app/struct.App.html#method.set_runner)
now has to return a `AppExit`.
-
[`App::run()`](https://docs.rs/bevy/latest/bevy/app/struct.App.html#method.run)
now also returns the `AppExit` produced by the runner function.


## Migration Guide

- Replace all usages of
[`AppExit`](https://docs.rs/bevy/latest/bevy/app/struct.AppExit.html)
with `AppExit::Success` or `AppExit::Failure`.
- Any custom app runners now need to return a `AppExit`. We suggest you
return a `AppExit::Error` if any `AppExit` raised was a Error. You can
use the new [`App::should_exit`](https://example.org/) method.
- If not exiting from `main` any other way. You should return the
`AppExit` from `App::run()` so the app correctly returns a error code if
anything fails e.g.
```rust
fn main() -> AppExit {
    App::new()
        //Your setup here...
        .run()
}
```

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-04-22 16:48:18 +00:00

44 lines
1.1 KiB
Rust

//! This example demonstrates you can create a custom runner (to update an app manually). It reads
//! lines from stdin and prints them from within the ecs.
use bevy::{app::AppExit, prelude::*};
use std::io;
#[derive(Resource)]
struct Input(String);
fn my_runner(mut app: App) -> AppExit {
println!("Type stuff into the console");
for line in io::stdin().lines() {
{
let mut input = app.world_mut().resource_mut::<Input>();
input.0 = line.unwrap();
}
app.update();
if let Some(exit) = app.should_exit() {
return exit;
}
}
AppExit::Success
}
fn print_system(input: Res<Input>) {
println!("You typed: {}", input.0);
}
fn exit_system(input: Res<Input>, mut exit_event: EventWriter<AppExit>) {
if input.0 == "exit" {
exit_event.send(AppExit::Success);
}
}
// AppExit implements `Termination` so we can return it from main.
fn main() -> AppExit {
App::new()
.insert_resource(Input(String::new()))
.set_runner(my_runner)
.add_systems(Update, (print_system, exit_system))
.run()
}