bevy/crates/bevy_reflect
Lura 856b39d821
Apply Clippy lints regarding lazy evaluation and closures (#14015)
# Objective

- Lazily evaluate
[default](https://rust-lang.github.io/rust-clippy/master/index.html#/unwrap_or_default)~~/[or](https://rust-lang.github.io/rust-clippy/master/index.html#/or_fun_call)~~
values where it makes sense
  - ~~`unwrap_or(foo())` -> `unwrap_or_else(|| foo())`~~
  - `unwrap_or(Default::default())` -> `unwrap_or_default()`
  - etc.
- Avoid creating [redundant
closures](https://rust-lang.github.io/rust-clippy/master/index.html#/redundant_closure),
even for [method
calls](https://rust-lang.github.io/rust-clippy/master/index.html#/redundant_closure_for_method_calls)
  - `map(|something| something.into())` -> `map(Into:into)`

## Solution

- Apply Clippy lints:
-
~~[or_fun_call](https://rust-lang.github.io/rust-clippy/master/index.html#/or_fun_call)~~
-
[unwrap_or_default](https://rust-lang.github.io/rust-clippy/master/index.html#/unwrap_or_default)
-
[redundant_closure_for_method_calls](https://rust-lang.github.io/rust-clippy/master/index.html#/redundant_closure_for_method_calls)
([redundant
closures](https://rust-lang.github.io/rust-clippy/master/index.html#/redundant_closure)
is already enabled)

## Testing

- Tested on Windows 11 (`stable-x86_64-pc-windows-gnu`, 1.79.0)
- Bevy compiles without errors or warnings and examples seem to work as
intended
  - `cargo clippy` 
  - `cargo run -p ci -- compile` 

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-07-01 15:54:40 +00:00
..
compile_fail bevy_reflect: Function reflection (#13152) 2024-07-01 13:49:08 +00:00
derive Apply Clippy lints regarding lazy evaluation and closures (#14015) 2024-07-01 15:54:40 +00:00
examples fix nightly clippy warnings (#6395) 2022-10-28 21:03:01 +00:00
src Apply Clippy lints regarding lazy evaluation and closures (#14015) 2024-07-01 15:54:40 +00:00
Cargo.toml Move bevy_math Reflect impls (#13520) 2024-05-27 14:15:22 +00:00
README.md add and fix shields in Readmes (#9993) 2023-10-15 00:52:31 +00:00

Bevy Reflect

License Crates.io Downloads Docs Discord

This crate enables you to dynamically interact with Rust types:

  • Derive the Reflect traits
  • Interact with fields using their names (for named structs) or indices (for tuple structs)
  • "Patch" your types with new values
  • Look up nested fields using "path strings"
  • Iterate over struct fields
  • Automatically serialize and deserialize via Serde (without explicit serde impls)
  • Trait "reflection"

Features

Derive the Reflect traits

// this will automatically implement the Reflect trait and the Struct trait (because the type is a struct)
#[derive(Reflect)]
struct Foo {
    a: u32,
    b: Bar,
    c: Vec<i32>,
    d: Vec<Baz>,
}

// this will automatically implement the Reflect trait and the TupleStruct trait (because the type is a tuple struct)
#[derive(Reflect)]
struct Bar(String);

#[derive(Reflect)]
struct Baz {
    value: f32,
}

// We will use this value to illustrate `bevy_reflect` features
let mut foo = Foo {
    a: 1,
    b: Bar("hello".to_string()),
    c: vec![1, 2],
    d: vec![Baz { value: 3.14 }],
};

Interact with fields using their names

assert_eq!(*foo.get_field::<u32>("a").unwrap(), 1);

*foo.get_field_mut::<u32>("a").unwrap() = 2;

assert_eq!(foo.a, 2);

"Patch" your types with new values

let mut dynamic_struct = DynamicStruct::default();
dynamic_struct.insert("a", 42u32);
dynamic_struct.insert("c", vec![3, 4, 5]);

foo.apply(&dynamic_struct);

assert_eq!(foo.a, 42);
assert_eq!(foo.c, vec![3, 4, 5]);

Look up nested fields using "path strings"

let value = *foo.get_path::<f32>("d[0].value").unwrap();
assert_eq!(value, 3.14);

Iterate over struct fields

for (i, value: &Reflect) in foo.iter_fields().enumerate() {
    let field_name = foo.name_at(i).unwrap();
    if let Some(value) = value.downcast_ref::<u32>() {
        println!("{} is a u32 with the value: {}", field_name, *value);
    }
}

Automatically serialize and deserialize via Serde (without explicit serde impls)

let mut registry = TypeRegistry::default();
registry.register::<u32>();
registry.register::<i32>();
registry.register::<f32>();
registry.register::<String>();
registry.register::<Bar>();
registry.register::<Baz>();

let serializer = ReflectSerializer::new(&foo, &registry);
let serialized = ron::ser::to_string_pretty(&serializer, ron::ser::PrettyConfig::default()).unwrap();

let mut deserializer = ron::de::Deserializer::from_str(&serialized).unwrap();
let reflect_deserializer = ReflectDeserializer::new(&registry);
let value = reflect_deserializer.deserialize(&mut deserializer).unwrap();
let dynamic_struct = value.take::<DynamicStruct>().unwrap();

assert!(foo.reflect_partial_eq(&dynamic_struct).unwrap());

Trait "reflection"

Call a trait on a given &dyn Reflect reference without knowing the underlying type!

#[derive(Reflect)]
#[reflect(DoThing)]
struct MyType {
    value: String,
}

impl DoThing for MyType {
    fn do_thing(&self) -> String {
        format!("{} World!", self.value)
    }
}

#[reflect_trait]
pub trait DoThing {
    fn do_thing(&self) -> String;
}

// First, lets box our type as a Box<dyn Reflect>
let reflect_value: Box<dyn Reflect> = Box::new(MyType {
    value: "Hello".to_string(),
});

// This means we no longer have direct access to MyType or its methods. We can only call Reflect methods on reflect_value.
// What if we want to call `do_thing` on our type? We could downcast using reflect_value.downcast_ref::<MyType>(), but what if we
// don't know the type at compile time?

// Normally in rust we would be out of luck at this point. Lets use our new reflection powers to do something cool!
let mut type_registry = TypeRegistry::default();
type_registry.register::<MyType>();

// The #[reflect] attribute we put on our DoThing trait generated a new `ReflectDoThing` struct, which implements TypeData.
// This was added to MyType's TypeRegistration.
let reflect_do_thing = type_registry
    .get_type_data::<ReflectDoThing>(reflect_value.type_id())
    .unwrap();

// We can use this generated type to convert our `&dyn Reflect` reference to a `&dyn DoThing` reference
let my_trait: &dyn DoThing = reflect_do_thing.get(&*reflect_value).unwrap();

// Which means we can now call do_thing(). Magic!
println!("{}", my_trait.do_thing());

// This works because the #[reflect(MyTrait)] we put on MyType informed the Reflect derive to insert a new instance
// of ReflectDoThing into MyType's registration. The instance knows how to cast &dyn Reflect to &dyn DoThing, because it
// knows that &dyn Reflect should first be downcasted to &MyType, which can then be safely casted to &dyn DoThing

Why make this?

The whole point of Rust is static safety! Why build something that makes it easy to throw it all away?

  • Some problems are inherently dynamic (scripting, some types of serialization / deserialization)
  • Sometimes the dynamic way is easier
  • Sometimes the dynamic way puts less burden on your users to derive a bunch of traits (this was a big motivator for the Bevy project)