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# Objective A common pattern in Rust is the [newtype](https://doc.rust-lang.org/rust-by-example/generics/new_types.html). This is an especially useful pattern in Bevy as it allows us to give common/foreign types different semantics (such as allowing it to implement `Component` or `FromWorld`) or to simply treat them as a "new type" (clever). For example, it allows us to wrap a common `Vec<String>` and do things like: ```rust #[derive(Component)] struct Items(Vec<String>); fn give_sword(query: Query<&mut Items>) { query.single_mut().0.push(String::from("Flaming Poisoning Raging Sword of Doom")); } ``` > We could then define another struct that wraps `Vec<String>` without anything clashing in the query. However, one of the worst parts of this pattern is the ugly `.0` we have to write in order to access the type we actually care about. This is why people often implement `Deref` and `DerefMut` in order to get around this. Since it's such a common pattern, especially for Bevy, it makes sense to add a derive macro to automatically add those implementations. ## Solution Added a derive macro for `Deref` and another for `DerefMut` (both exported into the prelude). This works on all structs (including tuple structs) as long as they only contain a single field: ```rust #[derive(Deref)] struct Foo(String); #[derive(Deref, DerefMut)] struct Bar { name: String, } ``` This allows us to then remove that pesky `.0`: ```rust #[derive(Component, Deref, DerefMut)] struct Items(Vec<String>); fn give_sword(query: Query<&mut Items>) { query.single_mut().push(String::from("Flaming Poisoning Raging Sword of Doom")); } ``` ### Alternatives There are other alternatives to this such as by using the [`derive_more`](https://crates.io/crates/derive_more) crate. However, it doesn't seem like we need an entire crate just yet since we only need `Deref` and `DerefMut` (for now). ### Considerations One thing to consider is that the Rust std library recommends _not_ using `Deref` and `DerefMut` for things like this: "`Deref` should only be implemented for smart pointers to avoid confusion" ([reference](https://doc.rust-lang.org/std/ops/trait.Deref.html)). Personally, I believe it makes sense to use it in the way described above, but others may disagree. ### Additional Context Discord: https://discord.com/channels/691052431525675048/692572690833473578/956648422163746827 (controversiality discussed [here](https://discord.com/channels/691052431525675048/692572690833473578/956711911481835630)) --- ## Changelog - Add `Deref` derive macro (exported to prelude) - Add `DerefMut` derive macro (exported to prelude) - Updated most newtypes in examples to use one or both derives Co-authored-by: MrGVSV <49806985+MrGVSV@users.noreply.github.com> |
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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 very early stages of development. APIs can and will change (now is the time to make suggestions!). Important features are missing. Documentation is sparse. Please don't build any serious projects in Bevy unless you are prepared to be broken by API changes constantly.
MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is "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.
- News: A development blog that covers our progress, plans and shiny new features.
Docs
- The Bevy Book: Bevy's official documentation. The best place to start learning Bevy.
- Bevy Rust API Docs: Bevy's Rust API docs, which are automatically generated from the doc comments in this repo.
- Official Examples: Bevy's dedicated, runnable examples, which are great for digging into specific concepts.
- Community-Made Learning Resources: More tutorials, documentation, and examples made by the Bevy community.
Community
Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.
- Discord: Bevy's official discord server.
- Reddit: Bevy's official subreddit.
- GitHub Discussions: The best place for questions about Bevy, answered right here!
- Bevy Assets: A collection of awesome Bevy projects, tools, plugins and learning materials.
If you'd like to help build Bevy, check out the Contributor's Guide. For simple problems, feel free to open an issue or PR and tackle it yourself!
For more complex architecture decisions and experimental mad science, please open an RFC (Request For Comments) so we can brainstorm together effectively!
Getting Started
We recommend checking out The Bevy Book for a full tutorial.
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
# Runs the "breakout" example
cargo run --example breakout
Fast Compiles
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.
Libraries Used
Bevy is only possible because of the hard work put into these foundational technologies:
- wgpu: modern / low-level / cross-platform graphics library inspired by Vulkan
- glam-rs: a simple and fast 3D math library for games and graphics
- winit: cross-platform window creation and management in Rust
- spirv-reflect: Reflection API in rust for SPIR-V shader byte code
Bevy Cargo Features
This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.
Third Party Plugins
Plugins are very welcome to extend Bevy's features. Guidelines are available to help integration and usage.
Thanks and Alternatives
Additionally, we would like to thank the Amethyst, macroquad, coffee, ggez, Fyrox, and Piston projects for providing solid examples of game engine development in Rust. If you are looking for a Rust game engine, it is worth considering all of your options. Each engine has different design goals, and some will likely resonate with you more than others.
License
Bevy is free and open source! All code in this repository is dual-licensed under either:
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
at your option. This means you can select the license you prefer! This dual-licensing approach is the de-facto standard in the Rust ecosystem and there are very good reasons to include both.
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.