da83232fa8
# Objective
The objective of this PR is to enable Components to use their
`MapEntities` implementation for `Component::map_entities`.
With the improvements to the entity mapping system, there is definitely
a huge reduction in boilerplate. However, especially since
`(Entity)HashMap<..>` doesn't implement `MapEntities` (I presume because
the lack of specialization in rust makes `HashMap<Entity|X, Entity|X>`
complicated), when somebody has types that contain these hashmaps they
can't use this approach.
More so, we can't even depend on the previous implementation, since
`Component::map_entities` is used instead of
`MapEntities::map_entities`. Outside of implementing `Component `and
`Component::map_entities` on these types directly, the only path forward
is to create a custom type to wrap the hashmaps and implement map
entities on that, or split these components into a wrapper type that
implement `Component`, and an inner type that implements `MapEntities`.
## Current Solution
The solution was to allow adding `#[component(map_entities)]` on the
component. By default this will defer to the `MapEntities`
implementation.
```rust
#[derive(Component)]
#[component(map_entities)]
struct Inventory {
items: HashMap<Entity, usize>
}
impl MapEntities for Inventory {
fn map_entities<M: EntityMapper>(&mut self, entity_mapper: &mut M) {
self.items = self.items
.drain()
.map(|(id, count)|(entity_mapper.get_mapped(id), count))
.collect();
}
}
```
You can use `#[component(map_entities = <function path>)]` instead to
substitute other code in for components. This function can also include
generics, but sso far I haven't been able to find a case where they are
needed.
```rust
#[derive(Component)]
#[component(map_entities = map_the_map)]
// Also works #[component(map_entities = map_the_map::<T,_>)]
struct Inventory<T> {
items: HashMap<Entity, T>
}
fn map_the_map<T, M: EntityMapper>(inv: &mut Inventory<T>, entity_mapper: &mut M) {
inv.items = inv.items
.drain()
.map(|(id, count)|(entity_mapper.get_mapped(id), count))
.collect();
}
```
The idea is that with the previous changes to MapEntities, MapEntities
is implemented more for entity collections than for Components. If you
have a component that makes sense as both, `#[component(map_entities)]`
would work great, while otherwise a component can use
`#[component(map_entities = <function>)]` to change the behavior of
`Component::map_entities` without opening up the component type to be
included in other components.
## (Original Solution if you want to follow the PR)
The solution was to allow adding `#[component(entities)]` on the
component itself to defer to the `MapEntities` implementation
```rust
#[derive(Component)]
#[component(entities)]
struct Inventory {
items: HashMap<Entity, usize>
}
impl MapEntities for Inventory {
fn map_entities<M: EntityMapper>(&mut self, entity_mapper: &mut M) {
self.items = self.items
.drain()
.map(|(id, count)|(entity_mapper.get_mapped(id), count))
.collect();
}
}
```
## Testing
I tested this by patching my local changes into my own bevy project. I
had a system that loads a scene file and executes some logic with a
Component that contains a `HashMap<Entity, UVec2>`, and it panics when
Entity is not found from another query. Since the 0.16 update this
system has reliably panicked upon attempting to the load the scene.
After patching my code in, I added `#[component(entities)]` to this
component, and I was able to successfully load the scene.
Additionally, I wrote a doc test.
## Call-outs
### Relationships
This overrules the default mapping of relationship fields. Anything else
seemed more problematic, as you'd have inconsistent behavior between
`MapEntities` and `Component`.
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| .github | ||
| assets | ||
| benches | ||
| crates | ||
| docs | ||
| docs-rs | ||
| docs-template | ||
| errors | ||
| examples | ||
| release-content | ||
| src | ||
| tests | ||
| tests-integration/simple-ecs-test | ||
| tools | ||
| .gitattributes | ||
| .gitignore | ||
| Cargo.toml | ||
| clippy.toml | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| CREDITS.md | ||
| deny.toml | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| README.md | ||
| rustfmt.toml | ||
| typos.toml | ||
What is Bevy?
Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!
WARNING
Bevy is still in the early stages of development. Important features are missing. Documentation is sparse. A new version of Bevy containing breaking changes to the API is released approximately once every 3 months. We provide migration guides, but we can't guarantee migrations will always be easy. Use only if you are willing to work in this environment.
MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is generally close to "the latest stable release" of Rust.
Design Goals
- Capable: Offer a complete 2D and 3D feature set
- Simple: Easy for newbies to pick up, but infinitely flexible for power users
- Data Focused: Data-oriented architecture using the Entity Component System paradigm
- Modular: Use only what you need. Replace what you don't like
- Fast: App logic should run quickly, and when possible, in parallel
- Productive: Changes should compile quickly ... waiting isn't fun
About
- Features: A quick overview of Bevy's features.
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- Quick Start Guide: Bevy's official Quick Start Guide. The best place to start learning Bevy.
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Getting Started
We recommend checking out the Quick Start Guide for a brief introduction.
Follow the Setup guide to ensure your development environment is set up correctly. Once set up, you can quickly try out the examples by cloning this repo and running the following commands:
# Switch to the correct version (latest release, default is main development branch)
git checkout latest
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cargo run --example breakout
To draw a window with standard functionality enabled, use:
use bevy::prelude::*;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.run();
}
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Bevy can be built just fine using default configuration on stable Rust. However for really fast iterative compiles, you should enable the "fast compiles" setup by following the instructions here.
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This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.
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This project is tested with BrowserStack.
License
Bevy is free, open source and permissively licensed! Except where noted (below and/or in individual files), all code in this repository is dual-licensed under either:
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
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Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.