bevy/crates/bevy_ecs/macros
Chris Russell 4be8e497ca
SystemParamBuilder - Allow deriving a SystemParamBuilder struct when deriving SystemParam. (#14818)
# Objective

Allow `SystemParamBuilder` implementations for custom system parameters
created using `#[derive(SystemParam)]`.

## Solution

Extend the derive macro to accept a `#[system_param(builder)]`
attribute. When present, emit a builder type with a field corresponding
to each field of the param.

## Example

```rust
#[derive(SystemParam)]
#[system_param(builder)]
struct CustomParam<'w, 's> {
    query: Query<'w, 's, ()>,
    local: Local<'s, usize>,
}

let system = (CustomParamBuilder {
    local: LocalBuilder(100),
    query: QueryParamBuilder::new(|builder| {
        builder.with::<A>();
    }),
},)
    .build_state(&mut world)
    .build_system(|param: CustomParam| *param.local + param.query.iter().count());
```
2024-08-28 18:24:52 +00:00
..
src SystemParamBuilder - Allow deriving a SystemParamBuilder struct when deriving SystemParam. (#14818) 2024-08-28 18:24:52 +00:00
Cargo.toml Generate links to definition in source code pages on docs.rs and dev-docs.bevyengine.org (#12965) 2024-07-29 23:10:16 +00:00